mirror of
https://github.com/rust-lang/rust.git
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yanchith
1842 lines
58 KiB
Rust
1842 lines
58 KiB
Rust
//! A priority queue implemented with a binary heap.
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//!
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//! Insertion and popping the largest element have *O*(log(*n*)) time complexity.
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//! Checking the largest element is *O*(1). Converting a vector to a binary heap
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//! can be done in-place, and has *O*(*n*) complexity. A binary heap can also be
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//! converted to a sorted vector in-place, allowing it to be used for an *O*(*n* * log(*n*))
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//! in-place heapsort.
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//!
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//! # Examples
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//!
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//! This is a larger example that implements [Dijkstra's algorithm][dijkstra]
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//! to solve the [shortest path problem][sssp] on a [directed graph][dir_graph].
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//! It shows how to use [`BinaryHeap`] with custom types.
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//!
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//! [dijkstra]: https://en.wikipedia.org/wiki/Dijkstra%27s_algorithm
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//! [sssp]: https://en.wikipedia.org/wiki/Shortest_path_problem
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//! [dir_graph]: https://en.wikipedia.org/wiki/Directed_graph
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//!
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//! ```
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//! use std::cmp::Ordering;
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//! use std::collections::BinaryHeap;
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//!
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//! #[derive(Copy, Clone, Eq, PartialEq)]
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//! struct State {
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//! cost: usize,
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//! position: usize,
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//! }
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//!
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//! // The priority queue depends on `Ord`.
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//! // Explicitly implement the trait so the queue becomes a min-heap
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//! // instead of a max-heap.
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//! impl Ord for State {
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//! fn cmp(&self, other: &Self) -> Ordering {
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//! // Notice that the we flip the ordering on costs.
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//! // In case of a tie we compare positions - this step is necessary
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//! // to make implementations of `PartialEq` and `Ord` consistent.
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//! other.cost.cmp(&self.cost)
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//! .then_with(|| self.position.cmp(&other.position))
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//! }
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//! }
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//!
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//! // `PartialOrd` needs to be implemented as well.
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//! impl PartialOrd for State {
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//! fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
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//! Some(self.cmp(other))
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//! }
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//! }
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//!
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//! // Each node is represented as a `usize`, for a shorter implementation.
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//! struct Edge {
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//! node: usize,
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//! cost: usize,
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//! }
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//!
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//! // Dijkstra's shortest path algorithm.
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//!
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//! // Start at `start` and use `dist` to track the current shortest distance
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//! // to each node. This implementation isn't memory-efficient as it may leave duplicate
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//! // nodes in the queue. It also uses `usize::MAX` as a sentinel value,
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//! // for a simpler implementation.
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//! fn shortest_path(adj_list: &Vec<Vec<Edge>>, start: usize, goal: usize) -> Option<usize> {
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//! // dist[node] = current shortest distance from `start` to `node`
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//! let mut dist: Vec<_> = (0..adj_list.len()).map(|_| usize::MAX).collect();
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//!
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//! let mut heap = BinaryHeap::new();
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//!
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//! // We're at `start`, with a zero cost
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//! dist[start] = 0;
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//! heap.push(State { cost: 0, position: start });
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//!
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//! // Examine the frontier with lower cost nodes first (min-heap)
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//! while let Some(State { cost, position }) = heap.pop() {
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//! // Alternatively we could have continued to find all shortest paths
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//! if position == goal { return Some(cost); }
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//!
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//! // Important as we may have already found a better way
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//! if cost > dist[position] { continue; }
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//!
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//! // For each node we can reach, see if we can find a way with
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//! // a lower cost going through this node
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//! for edge in &adj_list[position] {
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//! let next = State { cost: cost + edge.cost, position: edge.node };
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//!
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//! // If so, add it to the frontier and continue
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//! if next.cost < dist[next.position] {
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//! heap.push(next);
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//! // Relaxation, we have now found a better way
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//! dist[next.position] = next.cost;
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//! }
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//! }
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//! }
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//!
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//! // Goal not reachable
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//! None
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//! }
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//!
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//! fn main() {
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//! // This is the directed graph we're going to use.
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//! // The node numbers correspond to the different states,
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//! // and the edge weights symbolize the cost of moving
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//! // from one node to another.
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//! // Note that the edges are one-way.
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//! //
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//! // 7
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//! // +-----------------+
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//! // | |
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//! // v 1 2 | 2
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//! // 0 -----> 1 -----> 3 ---> 4
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//! // | ^ ^ ^
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//! // | | 1 | |
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//! // | | | 3 | 1
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//! // +------> 2 -------+ |
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//! // 10 | |
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//! // +---------------+
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//! //
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//! // The graph is represented as an adjacency list where each index,
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//! // corresponding to a node value, has a list of outgoing edges.
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//! // Chosen for its efficiency.
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//! let graph = vec![
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//! // Node 0
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//! vec![Edge { node: 2, cost: 10 },
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//! Edge { node: 1, cost: 1 }],
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//! // Node 1
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//! vec![Edge { node: 3, cost: 2 }],
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//! // Node 2
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//! vec![Edge { node: 1, cost: 1 },
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//! Edge { node: 3, cost: 3 },
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//! Edge { node: 4, cost: 1 }],
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//! // Node 3
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//! vec![Edge { node: 0, cost: 7 },
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//! Edge { node: 4, cost: 2 }],
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//! // Node 4
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//! vec![]];
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//!
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//! assert_eq!(shortest_path(&graph, 0, 1), Some(1));
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//! assert_eq!(shortest_path(&graph, 0, 3), Some(3));
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//! assert_eq!(shortest_path(&graph, 3, 0), Some(7));
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//! assert_eq!(shortest_path(&graph, 0, 4), Some(5));
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//! assert_eq!(shortest_path(&graph, 4, 0), None);
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//! }
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//! ```
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#![allow(missing_docs)]
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#![stable(feature = "rust1", since = "1.0.0")]
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use core::alloc::Allocator;
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use core::fmt;
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use core::iter::{FusedIterator, InPlaceIterable, SourceIter, TrustedLen};
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use core::mem::{self, swap, ManuallyDrop};
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use core::num::NonZeroUsize;
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use core::ops::{Deref, DerefMut};
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use core::ptr;
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use crate::alloc::Global;
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use crate::collections::TryReserveError;
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use crate::slice;
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use crate::vec::{self, AsVecIntoIter, Vec};
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#[cfg(test)]
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mod tests;
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/// A priority queue implemented with a binary heap.
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///
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/// This will be a max-heap.
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///
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/// It is a logic error for an item to be modified in such a way that the
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/// item's ordering relative to any other item, as determined by the [`Ord`]
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/// trait, changes while it is in the heap. This is normally only possible
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/// through interior mutability, global state, I/O, or unsafe code. The
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/// behavior resulting from such a logic error is not specified, but will
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/// be encapsulated to the `BinaryHeap` that observed the logic error and not
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/// result in undefined behavior. This could include panics, incorrect results,
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/// aborts, memory leaks, and non-termination.
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///
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/// As long as no elements change their relative order while being in the heap
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/// as described above, the API of `BinaryHeap` guarantees that the heap
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/// invariant remains intact i.e. its methods all behave as documented. For
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/// example if a method is documented as iterating in sorted order, that's
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/// guaranteed to work as long as elements in the heap have not changed order,
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/// even in the presence of closures getting unwinded out of, iterators getting
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/// leaked, and similar foolishness.
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///
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/// # Examples
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///
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/// ```
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/// use std::collections::BinaryHeap;
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///
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/// // Type inference lets us omit an explicit type signature (which
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/// // would be `BinaryHeap<i32>` in this example).
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/// let mut heap = BinaryHeap::new();
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///
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/// // We can use peek to look at the next item in the heap. In this case,
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/// // there's no items in there yet so we get None.
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/// assert_eq!(heap.peek(), None);
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///
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/// // Let's add some scores...
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/// heap.push(1);
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/// heap.push(5);
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/// heap.push(2);
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///
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/// // Now peek shows the most important item in the heap.
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/// assert_eq!(heap.peek(), Some(&5));
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///
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/// // We can check the length of a heap.
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/// assert_eq!(heap.len(), 3);
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///
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/// // We can iterate over the items in the heap, although they are returned in
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/// // a random order.
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/// for x in &heap {
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/// println!("{x}");
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/// }
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///
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/// // If we instead pop these scores, they should come back in order.
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/// assert_eq!(heap.pop(), Some(5));
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/// assert_eq!(heap.pop(), Some(2));
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/// assert_eq!(heap.pop(), Some(1));
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/// assert_eq!(heap.pop(), None);
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///
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/// // We can clear the heap of any remaining items.
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/// heap.clear();
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///
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/// // The heap should now be empty.
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/// assert!(heap.is_empty())
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/// ```
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///
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/// A `BinaryHeap` with a known list of items can be initialized from an array:
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///
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/// ```
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/// use std::collections::BinaryHeap;
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///
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/// let heap = BinaryHeap::from([1, 5, 2]);
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/// ```
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///
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/// ## Min-heap
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///
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/// Either [`core::cmp::Reverse`] or a custom [`Ord`] implementation can be used to
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/// make `BinaryHeap` a min-heap. This makes `heap.pop()` return the smallest
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/// value instead of the greatest one.
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///
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/// ```
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/// use std::collections::BinaryHeap;
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/// use std::cmp::Reverse;
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///
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/// let mut heap = BinaryHeap::new();
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///
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/// // Wrap values in `Reverse`
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/// heap.push(Reverse(1));
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/// heap.push(Reverse(5));
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/// heap.push(Reverse(2));
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///
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/// // If we pop these scores now, they should come back in the reverse order.
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/// assert_eq!(heap.pop(), Some(Reverse(1)));
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/// assert_eq!(heap.pop(), Some(Reverse(2)));
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/// assert_eq!(heap.pop(), Some(Reverse(5)));
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/// assert_eq!(heap.pop(), None);
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/// ```
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///
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/// # Time complexity
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///
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/// | [push] | [pop] | [peek]/[peek\_mut] |
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/// |---------|---------------|--------------------|
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/// | *O*(1)~ | *O*(log(*n*)) | *O*(1) |
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///
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/// The value for `push` is an expected cost; the method documentation gives a
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/// more detailed analysis.
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///
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/// [`core::cmp::Reverse`]: core::cmp::Reverse
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/// [`Cell`]: core::cell::Cell
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/// [`RefCell`]: core::cell::RefCell
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/// [push]: BinaryHeap::push
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/// [pop]: BinaryHeap::pop
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/// [peek]: BinaryHeap::peek
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/// [peek\_mut]: BinaryHeap::peek_mut
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#[stable(feature = "rust1", since = "1.0.0")]
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#[cfg_attr(not(test), rustc_diagnostic_item = "BinaryHeap")]
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pub struct BinaryHeap<
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T,
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#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
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> {
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data: Vec<T, A>,
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}
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/// Structure wrapping a mutable reference to the greatest item on a
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/// `BinaryHeap`.
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///
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/// This `struct` is created by the [`peek_mut`] method on [`BinaryHeap`]. See
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/// its documentation for more.
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///
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/// [`peek_mut`]: BinaryHeap::peek_mut
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#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
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pub struct PeekMut<
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'a,
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T: 'a + Ord,
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#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
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> {
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heap: &'a mut BinaryHeap<T, A>,
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// If a set_len + sift_down are required, this is Some. If a &mut T has not
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// yet been exposed to peek_mut()'s caller, it's None.
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original_len: Option<NonZeroUsize>,
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}
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#[stable(feature = "collection_debug", since = "1.17.0")]
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impl<'a, T: Ord + fmt::Debug, A: Allocator + 'a> fmt::Debug for PeekMut<'a, T, A> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_tuple("PeekMut").field(&self.heap.data[0]).finish()
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}
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}
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#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
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impl<'a, T: Ord, A: Allocator + 'a> Drop for PeekMut<'a, T, A> {
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fn drop(&mut self) {
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if let Some(original_len) = self.original_len {
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// SAFETY: That's how many elements were in the Vec at the time of
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// the PeekMut::deref_mut call, and therefore also at the time of
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// the BinaryHeap::peek_mut call. Since the PeekMut did not end up
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// getting leaked, we are now undoing the leak amplification that
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// the DerefMut prepared for.
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unsafe { self.heap.data.set_len(original_len.get()) };
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// SAFETY: PeekMut is only instantiated for non-empty heaps.
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unsafe { self.heap.sift_down(0) };
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}
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}
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}
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#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
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impl<'a, T: Ord, A: Allocator + 'a> Deref for PeekMut<'a, T, A> {
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type Target = T;
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fn deref(&self) -> &T {
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debug_assert!(!self.heap.is_empty());
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// SAFE: PeekMut is only instantiated for non-empty heaps
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unsafe { self.heap.data.get_unchecked(0) }
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}
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}
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#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
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impl<'a, T: Ord, A: Allocator + 'a> DerefMut for PeekMut<'a, T, A> {
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fn deref_mut(&mut self) -> &mut T {
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debug_assert!(!self.heap.is_empty());
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let len = self.heap.len();
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if len > 1 {
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// Here we preemptively leak all the rest of the underlying vector
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// after the currently max element. If the caller mutates the &mut T
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// we're about to give them, and then leaks the PeekMut, all these
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// elements will remain leaked. If they don't leak the PeekMut, then
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// either Drop or PeekMut::pop will un-leak the vector elements.
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//
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// This is technique is described throughout several other places in
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// the standard library as "leak amplification".
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unsafe {
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// SAFETY: len > 1 so len != 0.
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self.original_len = Some(NonZeroUsize::new_unchecked(len));
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// SAFETY: len > 1 so all this does for now is leak elements,
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// which is safe.
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self.heap.data.set_len(1);
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}
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}
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// SAFE: PeekMut is only instantiated for non-empty heaps
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unsafe { self.heap.data.get_unchecked_mut(0) }
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}
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}
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impl<'a, T: Ord, A: Allocator + 'a> PeekMut<'a, T, A> {
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/// Removes the peeked value from the heap and returns it.
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#[stable(feature = "binary_heap_peek_mut_pop", since = "1.18.0")]
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pub fn pop(mut this: PeekMut<'a, T, A>) -> T {
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if let Some(original_len) = this.original_len.take() {
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// SAFETY: This is how many elements were in the Vec at the time of
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// the BinaryHeap::peek_mut call.
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unsafe { this.heap.data.set_len(original_len.get()) };
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// Unlike in Drop, here we don't also need to do a sift_down even if
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// the caller could've mutated the element. It is removed from the
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// heap on the next line and pop() is not sensitive to its value.
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}
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this.heap.pop().unwrap()
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: Clone, A: Allocator + Clone> Clone for BinaryHeap<T, A> {
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fn clone(&self) -> Self {
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BinaryHeap { data: self.data.clone() }
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}
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fn clone_from(&mut self, source: &Self) {
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self.data.clone_from(&source.data);
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: Ord> Default for BinaryHeap<T> {
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/// Creates an empty `BinaryHeap<T>`.
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#[inline]
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fn default() -> BinaryHeap<T> {
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BinaryHeap::new()
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}
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}
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#[stable(feature = "binaryheap_debug", since = "1.4.0")]
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impl<T: fmt::Debug, A: Allocator> fmt::Debug for BinaryHeap<T, A> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_list().entries(self.iter()).finish()
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}
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}
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struct RebuildOnDrop<
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'a,
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T: Ord,
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#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
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> {
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heap: &'a mut BinaryHeap<T, A>,
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rebuild_from: usize,
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}
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impl<'a, T: Ord, A: Allocator> Drop for RebuildOnDrop<'a, T, A> {
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fn drop(&mut self) {
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self.heap.rebuild_tail(self.rebuild_from);
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}
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}
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impl<T: Ord> BinaryHeap<T> {
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/// Creates an empty `BinaryHeap` as a max-heap.
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///
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// use std::collections::BinaryHeap;
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/// let mut heap = BinaryHeap::new();
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/// heap.push(4);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[must_use]
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pub fn new() -> BinaryHeap<T> {
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BinaryHeap { data: vec![] }
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}
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/// Creates an empty `BinaryHeap` with at least the specified capacity.
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///
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/// The binary heap will be able to hold at least `capacity` elements without
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/// reallocating. This method is allowed to allocate for more elements than
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/// `capacity`. If `capacity` is 0, the binary heap will not allocate.
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///
|
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// use std::collections::BinaryHeap;
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/// let mut heap = BinaryHeap::with_capacity(10);
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/// heap.push(4);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[must_use]
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pub fn with_capacity(capacity: usize) -> BinaryHeap<T> {
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BinaryHeap { data: Vec::with_capacity(capacity) }
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}
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|
}
|
|
|
|
impl<T: Ord, A: Allocator> BinaryHeap<T, A> {
|
|
/// Creates an empty `BinaryHeap` as a max-heap, using `A` as allocator.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// #![feature(allocator_api)]
|
|
///
|
|
/// use std::alloc::System;
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap = BinaryHeap::new_in(System);
|
|
/// heap.push(4);
|
|
/// ```
|
|
#[unstable(feature = "allocator_api", issue = "32838")]
|
|
#[must_use]
|
|
pub fn new_in(alloc: A) -> BinaryHeap<T, A> {
|
|
BinaryHeap { data: Vec::new_in(alloc) }
|
|
}
|
|
|
|
/// Creates an empty `BinaryHeap` with at least the specified capacity, using `A` as allocator.
|
|
///
|
|
/// The binary heap will be able to hold at least `capacity` elements without
|
|
/// reallocating. This method is allowed to allocate for more elements than
|
|
/// `capacity`. If `capacity` is 0, the binary heap will not allocate.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// #![feature(allocator_api)]
|
|
///
|
|
/// use std::alloc::System;
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap = BinaryHeap::with_capacity_in(10, System);
|
|
/// heap.push(4);
|
|
/// ```
|
|
#[unstable(feature = "allocator_api", issue = "32838")]
|
|
#[must_use]
|
|
pub fn with_capacity_in(capacity: usize, alloc: A) -> BinaryHeap<T, A> {
|
|
BinaryHeap { data: Vec::with_capacity_in(capacity, alloc) }
|
|
}
|
|
|
|
/// Returns a mutable reference to the greatest item in the binary heap, or
|
|
/// `None` if it is empty.
|
|
///
|
|
/// Note: If the `PeekMut` value is leaked, some heap elements might get
|
|
/// leaked along with it, but the remaining elements will remain a valid
|
|
/// heap.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap = BinaryHeap::new();
|
|
/// assert!(heap.peek_mut().is_none());
|
|
///
|
|
/// heap.push(1);
|
|
/// heap.push(5);
|
|
/// heap.push(2);
|
|
/// {
|
|
/// let mut val = heap.peek_mut().unwrap();
|
|
/// *val = 0;
|
|
/// }
|
|
/// assert_eq!(heap.peek(), Some(&2));
|
|
/// ```
|
|
///
|
|
/// # Time complexity
|
|
///
|
|
/// If the item is modified then the worst case time complexity is *O*(log(*n*)),
|
|
/// otherwise it's *O*(1).
|
|
#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
|
|
pub fn peek_mut(&mut self) -> Option<PeekMut<'_, T, A>> {
|
|
if self.is_empty() {
|
|
None
|
|
} else {
|
|
Some(PeekMut { heap: self, original_len: None })
|
|
}
|
|
}
|
|
|
|
/// Removes the greatest item from the binary heap and returns it, or `None` if it
|
|
/// is empty.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap = BinaryHeap::from([1, 3]);
|
|
///
|
|
/// assert_eq!(heap.pop(), Some(3));
|
|
/// assert_eq!(heap.pop(), Some(1));
|
|
/// assert_eq!(heap.pop(), None);
|
|
/// ```
|
|
///
|
|
/// # Time complexity
|
|
///
|
|
/// The worst case cost of `pop` on a heap containing *n* elements is *O*(log(*n*)).
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn pop(&mut self) -> Option<T> {
|
|
self.data.pop().map(|mut item| {
|
|
if !self.is_empty() {
|
|
swap(&mut item, &mut self.data[0]);
|
|
// SAFETY: !self.is_empty() means that self.len() > 0
|
|
unsafe { self.sift_down_to_bottom(0) };
|
|
}
|
|
item
|
|
})
|
|
}
|
|
|
|
/// Pushes an item onto the binary heap.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap = BinaryHeap::new();
|
|
/// heap.push(3);
|
|
/// heap.push(5);
|
|
/// heap.push(1);
|
|
///
|
|
/// assert_eq!(heap.len(), 3);
|
|
/// assert_eq!(heap.peek(), Some(&5));
|
|
/// ```
|
|
///
|
|
/// # Time complexity
|
|
///
|
|
/// The expected cost of `push`, averaged over every possible ordering of
|
|
/// the elements being pushed, and over a sufficiently large number of
|
|
/// pushes, is *O*(1). This is the most meaningful cost metric when pushing
|
|
/// elements that are *not* already in any sorted pattern.
|
|
///
|
|
/// The time complexity degrades if elements are pushed in predominantly
|
|
/// ascending order. In the worst case, elements are pushed in ascending
|
|
/// sorted order and the amortized cost per push is *O*(log(*n*)) against a heap
|
|
/// containing *n* elements.
|
|
///
|
|
/// The worst case cost of a *single* call to `push` is *O*(*n*). The worst case
|
|
/// occurs when capacity is exhausted and needs a resize. The resize cost
|
|
/// has been amortized in the previous figures.
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn push(&mut self, item: T) {
|
|
let old_len = self.len();
|
|
self.data.push(item);
|
|
// SAFETY: Since we pushed a new item it means that
|
|
// old_len = self.len() - 1 < self.len()
|
|
unsafe { self.sift_up(0, old_len) };
|
|
}
|
|
|
|
/// Consumes the `BinaryHeap` and returns a vector in sorted
|
|
/// (ascending) order.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
///
|
|
/// let mut heap = BinaryHeap::from([1, 2, 4, 5, 7]);
|
|
/// heap.push(6);
|
|
/// heap.push(3);
|
|
///
|
|
/// let vec = heap.into_sorted_vec();
|
|
/// assert_eq!(vec, [1, 2, 3, 4, 5, 6, 7]);
|
|
/// ```
|
|
#[must_use = "`self` will be dropped if the result is not used"]
|
|
#[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
|
|
pub fn into_sorted_vec(mut self) -> Vec<T, A> {
|
|
let mut end = self.len();
|
|
while end > 1 {
|
|
end -= 1;
|
|
// SAFETY: `end` goes from `self.len() - 1` to 1 (both included),
|
|
// so it's always a valid index to access.
|
|
// It is safe to access index 0 (i.e. `ptr`), because
|
|
// 1 <= end < self.len(), which means self.len() >= 2.
|
|
unsafe {
|
|
let ptr = self.data.as_mut_ptr();
|
|
ptr::swap(ptr, ptr.add(end));
|
|
}
|
|
// SAFETY: `end` goes from `self.len() - 1` to 1 (both included) so:
|
|
// 0 < 1 <= end <= self.len() - 1 < self.len()
|
|
// Which means 0 < end and end < self.len().
|
|
unsafe { self.sift_down_range(0, end) };
|
|
}
|
|
self.into_vec()
|
|
}
|
|
|
|
// The implementations of sift_up and sift_down use unsafe blocks in
|
|
// order to move an element out of the vector (leaving behind a
|
|
// hole), shift along the others and move the removed element back into the
|
|
// vector at the final location of the hole.
|
|
// The `Hole` type is used to represent this, and make sure
|
|
// the hole is filled back at the end of its scope, even on panic.
|
|
// Using a hole reduces the constant factor compared to using swaps,
|
|
// which involves twice as many moves.
|
|
|
|
/// # Safety
|
|
///
|
|
/// The caller must guarantee that `pos < self.len()`.
|
|
unsafe fn sift_up(&mut self, start: usize, pos: usize) -> usize {
|
|
// Take out the value at `pos` and create a hole.
|
|
// SAFETY: The caller guarantees that pos < self.len()
|
|
let mut hole = unsafe { Hole::new(&mut self.data, pos) };
|
|
|
|
while hole.pos() > start {
|
|
let parent = (hole.pos() - 1) / 2;
|
|
|
|
// SAFETY: hole.pos() > start >= 0, which means hole.pos() > 0
|
|
// and so hole.pos() - 1 can't underflow.
|
|
// This guarantees that parent < hole.pos() so
|
|
// it's a valid index and also != hole.pos().
|
|
if hole.element() <= unsafe { hole.get(parent) } {
|
|
break;
|
|
}
|
|
|
|
// SAFETY: Same as above
|
|
unsafe { hole.move_to(parent) };
|
|
}
|
|
|
|
hole.pos()
|
|
}
|
|
|
|
/// Take an element at `pos` and move it down the heap,
|
|
/// while its children are larger.
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// The caller must guarantee that `pos < end <= self.len()`.
|
|
unsafe fn sift_down_range(&mut self, pos: usize, end: usize) {
|
|
// SAFETY: The caller guarantees that pos < end <= self.len().
|
|
let mut hole = unsafe { Hole::new(&mut self.data, pos) };
|
|
let mut child = 2 * hole.pos() + 1;
|
|
|
|
// Loop invariant: child == 2 * hole.pos() + 1.
|
|
while child <= end.saturating_sub(2) {
|
|
// compare with the greater of the two children
|
|
// SAFETY: child < end - 1 < self.len() and
|
|
// child + 1 < end <= self.len(), so they're valid indexes.
|
|
// child == 2 * hole.pos() + 1 != hole.pos() and
|
|
// child + 1 == 2 * hole.pos() + 2 != hole.pos().
|
|
// FIXME: 2 * hole.pos() + 1 or 2 * hole.pos() + 2 could overflow
|
|
// if T is a ZST
|
|
child += unsafe { hole.get(child) <= hole.get(child + 1) } as usize;
|
|
|
|
// if we are already in order, stop.
|
|
// SAFETY: child is now either the old child or the old child+1
|
|
// We already proven that both are < self.len() and != hole.pos()
|
|
if hole.element() >= unsafe { hole.get(child) } {
|
|
return;
|
|
}
|
|
|
|
// SAFETY: same as above.
|
|
unsafe { hole.move_to(child) };
|
|
child = 2 * hole.pos() + 1;
|
|
}
|
|
|
|
// SAFETY: && short circuit, which means that in the
|
|
// second condition it's already true that child == end - 1 < self.len().
|
|
if child == end - 1 && hole.element() < unsafe { hole.get(child) } {
|
|
// SAFETY: child is already proven to be a valid index and
|
|
// child == 2 * hole.pos() + 1 != hole.pos().
|
|
unsafe { hole.move_to(child) };
|
|
}
|
|
}
|
|
|
|
/// # Safety
|
|
///
|
|
/// The caller must guarantee that `pos < self.len()`.
|
|
unsafe fn sift_down(&mut self, pos: usize) {
|
|
let len = self.len();
|
|
// SAFETY: pos < len is guaranteed by the caller and
|
|
// obviously len = self.len() <= self.len().
|
|
unsafe { self.sift_down_range(pos, len) };
|
|
}
|
|
|
|
/// Take an element at `pos` and move it all the way down the heap,
|
|
/// then sift it up to its position.
|
|
///
|
|
/// Note: This is faster when the element is known to be large / should
|
|
/// be closer to the bottom.
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// The caller must guarantee that `pos < self.len()`.
|
|
unsafe fn sift_down_to_bottom(&mut self, mut pos: usize) {
|
|
let end = self.len();
|
|
let start = pos;
|
|
|
|
// SAFETY: The caller guarantees that pos < self.len().
|
|
let mut hole = unsafe { Hole::new(&mut self.data, pos) };
|
|
let mut child = 2 * hole.pos() + 1;
|
|
|
|
// Loop invariant: child == 2 * hole.pos() + 1.
|
|
while child <= end.saturating_sub(2) {
|
|
// SAFETY: child < end - 1 < self.len() and
|
|
// child + 1 < end <= self.len(), so they're valid indexes.
|
|
// child == 2 * hole.pos() + 1 != hole.pos() and
|
|
// child + 1 == 2 * hole.pos() + 2 != hole.pos().
|
|
// FIXME: 2 * hole.pos() + 1 or 2 * hole.pos() + 2 could overflow
|
|
// if T is a ZST
|
|
child += unsafe { hole.get(child) <= hole.get(child + 1) } as usize;
|
|
|
|
// SAFETY: Same as above
|
|
unsafe { hole.move_to(child) };
|
|
child = 2 * hole.pos() + 1;
|
|
}
|
|
|
|
if child == end - 1 {
|
|
// SAFETY: child == end - 1 < self.len(), so it's a valid index
|
|
// and child == 2 * hole.pos() + 1 != hole.pos().
|
|
unsafe { hole.move_to(child) };
|
|
}
|
|
pos = hole.pos();
|
|
drop(hole);
|
|
|
|
// SAFETY: pos is the position in the hole and was already proven
|
|
// to be a valid index.
|
|
unsafe { self.sift_up(start, pos) };
|
|
}
|
|
|
|
/// Rebuild assuming data[0..start] is still a proper heap.
|
|
fn rebuild_tail(&mut self, start: usize) {
|
|
if start == self.len() {
|
|
return;
|
|
}
|
|
|
|
let tail_len = self.len() - start;
|
|
|
|
#[inline(always)]
|
|
fn log2_fast(x: usize) -> usize {
|
|
(usize::BITS - x.leading_zeros() - 1) as usize
|
|
}
|
|
|
|
// `rebuild` takes O(self.len()) operations
|
|
// and about 2 * self.len() comparisons in the worst case
|
|
// while repeating `sift_up` takes O(tail_len * log(start)) operations
|
|
// and about 1 * tail_len * log_2(start) comparisons in the worst case,
|
|
// assuming start >= tail_len. For larger heaps, the crossover point
|
|
// no longer follows this reasoning and was determined empirically.
|
|
let better_to_rebuild = if start < tail_len {
|
|
true
|
|
} else if self.len() <= 2048 {
|
|
2 * self.len() < tail_len * log2_fast(start)
|
|
} else {
|
|
2 * self.len() < tail_len * 11
|
|
};
|
|
|
|
if better_to_rebuild {
|
|
self.rebuild();
|
|
} else {
|
|
for i in start..self.len() {
|
|
// SAFETY: The index `i` is always less than self.len().
|
|
unsafe { self.sift_up(0, i) };
|
|
}
|
|
}
|
|
}
|
|
|
|
fn rebuild(&mut self) {
|
|
let mut n = self.len() / 2;
|
|
while n > 0 {
|
|
n -= 1;
|
|
// SAFETY: n starts from self.len() / 2 and goes down to 0.
|
|
// The only case when !(n < self.len()) is if
|
|
// self.len() == 0, but it's ruled out by the loop condition.
|
|
unsafe { self.sift_down(n) };
|
|
}
|
|
}
|
|
|
|
/// Moves all the elements of `other` into `self`, leaving `other` empty.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
///
|
|
/// let mut a = BinaryHeap::from([-10, 1, 2, 3, 3]);
|
|
/// let mut b = BinaryHeap::from([-20, 5, 43]);
|
|
///
|
|
/// a.append(&mut b);
|
|
///
|
|
/// assert_eq!(a.into_sorted_vec(), [-20, -10, 1, 2, 3, 3, 5, 43]);
|
|
/// assert!(b.is_empty());
|
|
/// ```
|
|
#[stable(feature = "binary_heap_append", since = "1.11.0")]
|
|
pub fn append(&mut self, other: &mut Self) {
|
|
if self.len() < other.len() {
|
|
swap(self, other);
|
|
}
|
|
|
|
let start = self.data.len();
|
|
|
|
self.data.append(&mut other.data);
|
|
|
|
self.rebuild_tail(start);
|
|
}
|
|
|
|
/// Clears the binary heap, returning an iterator over the removed elements
|
|
/// in heap order. If the iterator is dropped before being fully consumed,
|
|
/// it drops the remaining elements in heap order.
|
|
///
|
|
/// The returned iterator keeps a mutable borrow on the heap to optimize
|
|
/// its implementation.
|
|
///
|
|
/// Note:
|
|
/// * `.drain_sorted()` is *O*(*n* \* log(*n*)); much slower than `.drain()`.
|
|
/// You should use the latter for most cases.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// #![feature(binary_heap_drain_sorted)]
|
|
/// use std::collections::BinaryHeap;
|
|
///
|
|
/// let mut heap = BinaryHeap::from([1, 2, 3, 4, 5]);
|
|
/// assert_eq!(heap.len(), 5);
|
|
///
|
|
/// drop(heap.drain_sorted()); // removes all elements in heap order
|
|
/// assert_eq!(heap.len(), 0);
|
|
/// ```
|
|
#[inline]
|
|
#[unstable(feature = "binary_heap_drain_sorted", issue = "59278")]
|
|
pub fn drain_sorted(&mut self) -> DrainSorted<'_, T, A> {
|
|
DrainSorted { inner: self }
|
|
}
|
|
|
|
/// Retains only the elements specified by the predicate.
|
|
///
|
|
/// In other words, remove all elements `e` for which `f(&e)` returns
|
|
/// `false`. The elements are visited in unsorted (and unspecified) order.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
///
|
|
/// let mut heap = BinaryHeap::from([-10, -5, 1, 2, 4, 13]);
|
|
///
|
|
/// heap.retain(|x| x % 2 == 0); // only keep even numbers
|
|
///
|
|
/// assert_eq!(heap.into_sorted_vec(), [-10, 2, 4])
|
|
/// ```
|
|
#[stable(feature = "binary_heap_retain", since = "1.70.0")]
|
|
pub fn retain<F>(&mut self, mut f: F)
|
|
where
|
|
F: FnMut(&T) -> bool,
|
|
{
|
|
// rebuild_start will be updated to the first touched element below, and the rebuild will
|
|
// only be done for the tail.
|
|
let mut guard = RebuildOnDrop { rebuild_from: self.len(), heap: self };
|
|
let mut i = 0;
|
|
|
|
guard.heap.data.retain(|e| {
|
|
let keep = f(e);
|
|
if !keep && i < guard.rebuild_from {
|
|
guard.rebuild_from = i;
|
|
}
|
|
i += 1;
|
|
keep
|
|
});
|
|
}
|
|
}
|
|
|
|
impl<T, A: Allocator> BinaryHeap<T, A> {
|
|
/// Returns an iterator visiting all values in the underlying vector, in
|
|
/// arbitrary order.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let heap = BinaryHeap::from([1, 2, 3, 4]);
|
|
///
|
|
/// // Print 1, 2, 3, 4 in arbitrary order
|
|
/// for x in heap.iter() {
|
|
/// println!("{x}");
|
|
/// }
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn iter(&self) -> Iter<'_, T> {
|
|
Iter { iter: self.data.iter() }
|
|
}
|
|
|
|
/// Returns an iterator which retrieves elements in heap order.
|
|
/// This method consumes the original heap.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// #![feature(binary_heap_into_iter_sorted)]
|
|
/// use std::collections::BinaryHeap;
|
|
/// let heap = BinaryHeap::from([1, 2, 3, 4, 5]);
|
|
///
|
|
/// assert_eq!(heap.into_iter_sorted().take(2).collect::<Vec<_>>(), [5, 4]);
|
|
/// ```
|
|
#[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")]
|
|
pub fn into_iter_sorted(self) -> IntoIterSorted<T, A> {
|
|
IntoIterSorted { inner: self }
|
|
}
|
|
|
|
/// Returns the greatest item in the binary heap, or `None` if it is empty.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap = BinaryHeap::new();
|
|
/// assert_eq!(heap.peek(), None);
|
|
///
|
|
/// heap.push(1);
|
|
/// heap.push(5);
|
|
/// heap.push(2);
|
|
/// assert_eq!(heap.peek(), Some(&5));
|
|
///
|
|
/// ```
|
|
///
|
|
/// # Time complexity
|
|
///
|
|
/// Cost is *O*(1) in the worst case.
|
|
#[must_use]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn peek(&self) -> Option<&T> {
|
|
self.data.get(0)
|
|
}
|
|
|
|
/// Returns the number of elements the binary heap can hold without reallocating.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap = BinaryHeap::with_capacity(100);
|
|
/// assert!(heap.capacity() >= 100);
|
|
/// heap.push(4);
|
|
/// ```
|
|
#[must_use]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn capacity(&self) -> usize {
|
|
self.data.capacity()
|
|
}
|
|
|
|
/// Reserves the minimum capacity for at least `additional` elements more than
|
|
/// the current length. Unlike [`reserve`], this will not
|
|
/// deliberately over-allocate to speculatively avoid frequent allocations.
|
|
/// After calling `reserve_exact`, capacity will be greater than or equal to
|
|
/// `self.len() + additional`. Does nothing if the capacity is already
|
|
/// sufficient.
|
|
///
|
|
/// [`reserve`]: BinaryHeap::reserve
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// Panics if the new capacity overflows [`usize`].
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap = BinaryHeap::new();
|
|
/// heap.reserve_exact(100);
|
|
/// assert!(heap.capacity() >= 100);
|
|
/// heap.push(4);
|
|
/// ```
|
|
///
|
|
/// [`reserve`]: BinaryHeap::reserve
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn reserve_exact(&mut self, additional: usize) {
|
|
self.data.reserve_exact(additional);
|
|
}
|
|
|
|
/// Reserves capacity for at least `additional` elements more than the
|
|
/// current length. The allocator may reserve more space to speculatively
|
|
/// avoid frequent allocations. After calling `reserve`,
|
|
/// capacity will be greater than or equal to `self.len() + additional`.
|
|
/// Does nothing if capacity is already sufficient.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// Panics if the new capacity overflows [`usize`].
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap = BinaryHeap::new();
|
|
/// heap.reserve(100);
|
|
/// assert!(heap.capacity() >= 100);
|
|
/// heap.push(4);
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn reserve(&mut self, additional: usize) {
|
|
self.data.reserve(additional);
|
|
}
|
|
|
|
/// Tries to reserve the minimum capacity for at least `additional` elements
|
|
/// more than the current length. Unlike [`try_reserve`], this will not
|
|
/// deliberately over-allocate to speculatively avoid frequent allocations.
|
|
/// After calling `try_reserve_exact`, capacity will be greater than or
|
|
/// equal to `self.len() + additional` if it returns `Ok(())`.
|
|
/// Does nothing if the capacity is already sufficient.
|
|
///
|
|
/// Note that the allocator may give the collection more space than it
|
|
/// requests. Therefore, capacity can not be relied upon to be precisely
|
|
/// minimal. Prefer [`try_reserve`] if future insertions are expected.
|
|
///
|
|
/// [`try_reserve`]: BinaryHeap::try_reserve
|
|
///
|
|
/// # Errors
|
|
///
|
|
/// If the capacity overflows, or the allocator reports a failure, then an error
|
|
/// is returned.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// use std::collections::TryReserveError;
|
|
///
|
|
/// fn find_max_slow(data: &[u32]) -> Result<Option<u32>, TryReserveError> {
|
|
/// let mut heap = BinaryHeap::new();
|
|
///
|
|
/// // Pre-reserve the memory, exiting if we can't
|
|
/// heap.try_reserve_exact(data.len())?;
|
|
///
|
|
/// // Now we know this can't OOM in the middle of our complex work
|
|
/// heap.extend(data.iter());
|
|
///
|
|
/// Ok(heap.pop())
|
|
/// }
|
|
/// # find_max_slow(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?");
|
|
/// ```
|
|
#[stable(feature = "try_reserve_2", since = "1.63.0")]
|
|
pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> {
|
|
self.data.try_reserve_exact(additional)
|
|
}
|
|
|
|
/// Tries to reserve capacity for at least `additional` elements more than the
|
|
/// current length. The allocator may reserve more space to speculatively
|
|
/// avoid frequent allocations. After calling `try_reserve`, capacity will be
|
|
/// greater than or equal to `self.len() + additional` if it returns
|
|
/// `Ok(())`. Does nothing if capacity is already sufficient. This method
|
|
/// preserves the contents even if an error occurs.
|
|
///
|
|
/// # Errors
|
|
///
|
|
/// If the capacity overflows, or the allocator reports a failure, then an error
|
|
/// is returned.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// use std::collections::TryReserveError;
|
|
///
|
|
/// fn find_max_slow(data: &[u32]) -> Result<Option<u32>, TryReserveError> {
|
|
/// let mut heap = BinaryHeap::new();
|
|
///
|
|
/// // Pre-reserve the memory, exiting if we can't
|
|
/// heap.try_reserve(data.len())?;
|
|
///
|
|
/// // Now we know this can't OOM in the middle of our complex work
|
|
/// heap.extend(data.iter());
|
|
///
|
|
/// Ok(heap.pop())
|
|
/// }
|
|
/// # find_max_slow(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?");
|
|
/// ```
|
|
#[stable(feature = "try_reserve_2", since = "1.63.0")]
|
|
pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
|
|
self.data.try_reserve(additional)
|
|
}
|
|
|
|
/// Discards as much additional capacity as possible.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap: BinaryHeap<i32> = BinaryHeap::with_capacity(100);
|
|
///
|
|
/// assert!(heap.capacity() >= 100);
|
|
/// heap.shrink_to_fit();
|
|
/// assert!(heap.capacity() == 0);
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn shrink_to_fit(&mut self) {
|
|
self.data.shrink_to_fit();
|
|
}
|
|
|
|
/// Discards capacity with a lower bound.
|
|
///
|
|
/// The capacity will remain at least as large as both the length
|
|
/// and the supplied value.
|
|
///
|
|
/// If the current capacity is less than the lower limit, this is a no-op.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap: BinaryHeap<i32> = BinaryHeap::with_capacity(100);
|
|
///
|
|
/// assert!(heap.capacity() >= 100);
|
|
/// heap.shrink_to(10);
|
|
/// assert!(heap.capacity() >= 10);
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "shrink_to", since = "1.56.0")]
|
|
pub fn shrink_to(&mut self, min_capacity: usize) {
|
|
self.data.shrink_to(min_capacity)
|
|
}
|
|
|
|
/// Returns a slice of all values in the underlying vector, in arbitrary
|
|
/// order.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// #![feature(binary_heap_as_slice)]
|
|
/// use std::collections::BinaryHeap;
|
|
/// use std::io::{self, Write};
|
|
///
|
|
/// let heap = BinaryHeap::from([1, 2, 3, 4, 5, 6, 7]);
|
|
///
|
|
/// io::sink().write(heap.as_slice()).unwrap();
|
|
/// ```
|
|
#[must_use]
|
|
#[unstable(feature = "binary_heap_as_slice", issue = "83659")]
|
|
pub fn as_slice(&self) -> &[T] {
|
|
self.data.as_slice()
|
|
}
|
|
|
|
/// Consumes the `BinaryHeap` and returns the underlying vector
|
|
/// in arbitrary order.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let heap = BinaryHeap::from([1, 2, 3, 4, 5, 6, 7]);
|
|
/// let vec = heap.into_vec();
|
|
///
|
|
/// // Will print in some order
|
|
/// for x in vec {
|
|
/// println!("{x}");
|
|
/// }
|
|
/// ```
|
|
#[must_use = "`self` will be dropped if the result is not used"]
|
|
#[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
|
|
pub fn into_vec(self) -> Vec<T, A> {
|
|
self.into()
|
|
}
|
|
|
|
/// Returns a reference to the underlying allocator.
|
|
#[unstable(feature = "allocator_api", issue = "32838")]
|
|
#[inline]
|
|
pub fn allocator(&self) -> &A {
|
|
self.data.allocator()
|
|
}
|
|
|
|
/// Returns the length of the binary heap.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let heap = BinaryHeap::from([1, 3]);
|
|
///
|
|
/// assert_eq!(heap.len(), 2);
|
|
/// ```
|
|
#[must_use]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn len(&self) -> usize {
|
|
self.data.len()
|
|
}
|
|
|
|
/// Checks if the binary heap is empty.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap = BinaryHeap::new();
|
|
///
|
|
/// assert!(heap.is_empty());
|
|
///
|
|
/// heap.push(3);
|
|
/// heap.push(5);
|
|
/// heap.push(1);
|
|
///
|
|
/// assert!(!heap.is_empty());
|
|
/// ```
|
|
#[must_use]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn is_empty(&self) -> bool {
|
|
self.len() == 0
|
|
}
|
|
|
|
/// Clears the binary heap, returning an iterator over the removed elements
|
|
/// in arbitrary order. If the iterator is dropped before being fully
|
|
/// consumed, it drops the remaining elements in arbitrary order.
|
|
///
|
|
/// The returned iterator keeps a mutable borrow on the heap to optimize
|
|
/// its implementation.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap = BinaryHeap::from([1, 3]);
|
|
///
|
|
/// assert!(!heap.is_empty());
|
|
///
|
|
/// for x in heap.drain() {
|
|
/// println!("{x}");
|
|
/// }
|
|
///
|
|
/// assert!(heap.is_empty());
|
|
/// ```
|
|
#[inline]
|
|
#[stable(feature = "drain", since = "1.6.0")]
|
|
pub fn drain(&mut self) -> Drain<'_, T, A> {
|
|
Drain { iter: self.data.drain(..) }
|
|
}
|
|
|
|
/// Drops all items from the binary heap.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let mut heap = BinaryHeap::from([1, 3]);
|
|
///
|
|
/// assert!(!heap.is_empty());
|
|
///
|
|
/// heap.clear();
|
|
///
|
|
/// assert!(heap.is_empty());
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub fn clear(&mut self) {
|
|
self.drain();
|
|
}
|
|
}
|
|
|
|
/// Hole represents a hole in a slice i.e., an index without valid value
|
|
/// (because it was moved from or duplicated).
|
|
/// In drop, `Hole` will restore the slice by filling the hole
|
|
/// position with the value that was originally removed.
|
|
struct Hole<'a, T: 'a> {
|
|
data: &'a mut [T],
|
|
elt: ManuallyDrop<T>,
|
|
pos: usize,
|
|
}
|
|
|
|
impl<'a, T> Hole<'a, T> {
|
|
/// Create a new `Hole` at index `pos`.
|
|
///
|
|
/// Unsafe because pos must be within the data slice.
|
|
#[inline]
|
|
unsafe fn new(data: &'a mut [T], pos: usize) -> Self {
|
|
debug_assert!(pos < data.len());
|
|
// SAFE: pos should be inside the slice
|
|
let elt = unsafe { ptr::read(data.get_unchecked(pos)) };
|
|
Hole { data, elt: ManuallyDrop::new(elt), pos }
|
|
}
|
|
|
|
#[inline]
|
|
fn pos(&self) -> usize {
|
|
self.pos
|
|
}
|
|
|
|
/// Returns a reference to the element removed.
|
|
#[inline]
|
|
fn element(&self) -> &T {
|
|
&self.elt
|
|
}
|
|
|
|
/// Returns a reference to the element at `index`.
|
|
///
|
|
/// Unsafe because index must be within the data slice and not equal to pos.
|
|
#[inline]
|
|
unsafe fn get(&self, index: usize) -> &T {
|
|
debug_assert!(index != self.pos);
|
|
debug_assert!(index < self.data.len());
|
|
unsafe { self.data.get_unchecked(index) }
|
|
}
|
|
|
|
/// Move hole to new location
|
|
///
|
|
/// Unsafe because index must be within the data slice and not equal to pos.
|
|
#[inline]
|
|
unsafe fn move_to(&mut self, index: usize) {
|
|
debug_assert!(index != self.pos);
|
|
debug_assert!(index < self.data.len());
|
|
unsafe {
|
|
let ptr = self.data.as_mut_ptr();
|
|
let index_ptr: *const _ = ptr.add(index);
|
|
let hole_ptr = ptr.add(self.pos);
|
|
ptr::copy_nonoverlapping(index_ptr, hole_ptr, 1);
|
|
}
|
|
self.pos = index;
|
|
}
|
|
}
|
|
|
|
impl<T> Drop for Hole<'_, T> {
|
|
#[inline]
|
|
fn drop(&mut self) {
|
|
// fill the hole again
|
|
unsafe {
|
|
let pos = self.pos;
|
|
ptr::copy_nonoverlapping(&*self.elt, self.data.get_unchecked_mut(pos), 1);
|
|
}
|
|
}
|
|
}
|
|
|
|
/// An iterator over the elements of a `BinaryHeap`.
|
|
///
|
|
/// This `struct` is created by [`BinaryHeap::iter()`]. See its
|
|
/// documentation for more.
|
|
///
|
|
/// [`iter`]: BinaryHeap::iter
|
|
#[must_use = "iterators are lazy and do nothing unless consumed"]
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
pub struct Iter<'a, T: 'a> {
|
|
iter: slice::Iter<'a, T>,
|
|
}
|
|
|
|
#[stable(feature = "collection_debug", since = "1.17.0")]
|
|
impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
f.debug_tuple("Iter").field(&self.iter.as_slice()).finish()
|
|
}
|
|
}
|
|
|
|
// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T> Clone for Iter<'_, T> {
|
|
fn clone(&self) -> Self {
|
|
Iter { iter: self.iter.clone() }
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<'a, T> Iterator for Iter<'a, T> {
|
|
type Item = &'a T;
|
|
|
|
#[inline]
|
|
fn next(&mut self) -> Option<&'a T> {
|
|
self.iter.next()
|
|
}
|
|
|
|
#[inline]
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
self.iter.size_hint()
|
|
}
|
|
|
|
#[inline]
|
|
fn last(self) -> Option<&'a T> {
|
|
self.iter.last()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
|
|
#[inline]
|
|
fn next_back(&mut self) -> Option<&'a T> {
|
|
self.iter.next_back()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T> ExactSizeIterator for Iter<'_, T> {
|
|
fn is_empty(&self) -> bool {
|
|
self.iter.is_empty()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "fused", since = "1.26.0")]
|
|
impl<T> FusedIterator for Iter<'_, T> {}
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|
|
|
/// An owning iterator over the elements of a `BinaryHeap`.
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|
///
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/// This `struct` is created by [`BinaryHeap::into_iter()`]
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/// (provided by the [`IntoIterator`] trait). See its documentation for more.
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///
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/// [`into_iter`]: BinaryHeap::into_iter
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|
#[stable(feature = "rust1", since = "1.0.0")]
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|
#[derive(Clone)]
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|
pub struct IntoIter<
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|
T,
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|
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
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|
> {
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iter: vec::IntoIter<T, A>,
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|
}
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|
|
|
#[stable(feature = "collection_debug", since = "1.17.0")]
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impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> {
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|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_tuple("IntoIter").field(&self.iter.as_slice()).finish()
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|
}
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|
}
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|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
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impl<T, A: Allocator> Iterator for IntoIter<T, A> {
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type Item = T;
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|
|
|
#[inline]
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|
fn next(&mut self) -> Option<T> {
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|
self.iter.next()
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|
}
|
|
|
|
#[inline]
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|
fn size_hint(&self) -> (usize, Option<usize>) {
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|
self.iter.size_hint()
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|
}
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|
}
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|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
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|
impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
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|
#[inline]
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|
fn next_back(&mut self) -> Option<T> {
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|
self.iter.next_back()
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|
}
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|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
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|
impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> {
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|
fn is_empty(&self) -> bool {
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|
self.iter.is_empty()
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|
}
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|
}
|
|
|
|
#[stable(feature = "fused", since = "1.26.0")]
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|
impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {}
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|
|
|
#[stable(feature = "default_iters", since = "1.70.0")]
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impl<T> Default for IntoIter<T> {
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|
/// Creates an empty `binary_heap::IntoIter`.
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|
///
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|
/// ```
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|
/// # use std::collections::binary_heap;
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|
/// let iter: binary_heap::IntoIter<u8> = Default::default();
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|
/// assert_eq!(iter.len(), 0);
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|
/// ```
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|
fn default() -> Self {
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|
IntoIter { iter: Default::default() }
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|
}
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|
}
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|
|
|
// In addition to the SAFETY invariants of the following three unsafe traits
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|
// also refer to the vec::in_place_collect module documentation to get an overview
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|
#[unstable(issue = "none", feature = "inplace_iteration")]
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|
#[doc(hidden)]
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|
unsafe impl<T, A: Allocator> SourceIter for IntoIter<T, A> {
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|
type Source = IntoIter<T, A>;
|
|
|
|
#[inline]
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|
unsafe fn as_inner(&mut self) -> &mut Self::Source {
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|
self
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|
}
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|
}
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|
|
|
#[unstable(issue = "none", feature = "inplace_iteration")]
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|
#[doc(hidden)]
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|
unsafe impl<I, A: Allocator> InPlaceIterable for IntoIter<I, A> {}
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|
|
|
unsafe impl<I> AsVecIntoIter for IntoIter<I, Global> {
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|
type Item = I;
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|
|
|
fn as_into_iter(&mut self) -> &mut vec::IntoIter<Self::Item> {
|
|
&mut self.iter
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|
}
|
|
}
|
|
|
|
#[must_use = "iterators are lazy and do nothing unless consumed"]
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|
#[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")]
|
|
#[derive(Clone, Debug)]
|
|
pub struct IntoIterSorted<
|
|
T,
|
|
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
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|
> {
|
|
inner: BinaryHeap<T, A>,
|
|
}
|
|
|
|
#[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")]
|
|
impl<T: Ord, A: Allocator> Iterator for IntoIterSorted<T, A> {
|
|
type Item = T;
|
|
|
|
#[inline]
|
|
fn next(&mut self) -> Option<T> {
|
|
self.inner.pop()
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|
}
|
|
|
|
#[inline]
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
let exact = self.inner.len();
|
|
(exact, Some(exact))
|
|
}
|
|
}
|
|
|
|
#[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")]
|
|
impl<T: Ord, A: Allocator> ExactSizeIterator for IntoIterSorted<T, A> {}
|
|
|
|
#[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")]
|
|
impl<T: Ord, A: Allocator> FusedIterator for IntoIterSorted<T, A> {}
|
|
|
|
#[unstable(feature = "trusted_len", issue = "37572")]
|
|
unsafe impl<T: Ord, A: Allocator> TrustedLen for IntoIterSorted<T, A> {}
|
|
|
|
/// A draining iterator over the elements of a `BinaryHeap`.
|
|
///
|
|
/// This `struct` is created by [`BinaryHeap::drain()`]. See its
|
|
/// documentation for more.
|
|
///
|
|
/// [`drain`]: BinaryHeap::drain
|
|
#[stable(feature = "drain", since = "1.6.0")]
|
|
#[derive(Debug)]
|
|
pub struct Drain<
|
|
'a,
|
|
T: 'a,
|
|
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + 'a = Global,
|
|
> {
|
|
iter: vec::Drain<'a, T, A>,
|
|
}
|
|
|
|
#[stable(feature = "drain", since = "1.6.0")]
|
|
impl<'a, T, A: Allocator + 'a> Iterator for Drain<'a, T, A> {
|
|
type Item = T;
|
|
|
|
#[inline]
|
|
fn next(&mut self) -> Option<T> {
|
|
self.iter.next()
|
|
}
|
|
|
|
#[inline]
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
self.iter.size_hint()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "drain", since = "1.6.0")]
|
|
impl<'a, T, A: Allocator + 'a> DoubleEndedIterator for Drain<'a, T, A> {
|
|
#[inline]
|
|
fn next_back(&mut self) -> Option<T> {
|
|
self.iter.next_back()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "drain", since = "1.6.0")]
|
|
impl<'a, T, A: Allocator + 'a> ExactSizeIterator for Drain<'a, T, A> {
|
|
fn is_empty(&self) -> bool {
|
|
self.iter.is_empty()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "fused", since = "1.26.0")]
|
|
impl<'a, T, A: Allocator + 'a> FusedIterator for Drain<'a, T, A> {}
|
|
|
|
/// A draining iterator over the elements of a `BinaryHeap`.
|
|
///
|
|
/// This `struct` is created by [`BinaryHeap::drain_sorted()`]. See its
|
|
/// documentation for more.
|
|
///
|
|
/// [`drain_sorted`]: BinaryHeap::drain_sorted
|
|
#[unstable(feature = "binary_heap_drain_sorted", issue = "59278")]
|
|
#[derive(Debug)]
|
|
pub struct DrainSorted<
|
|
'a,
|
|
T: Ord,
|
|
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + 'a = Global,
|
|
> {
|
|
inner: &'a mut BinaryHeap<T, A>,
|
|
}
|
|
|
|
#[unstable(feature = "binary_heap_drain_sorted", issue = "59278")]
|
|
impl<'a, T: Ord, A: Allocator + 'a> Drop for DrainSorted<'a, T, A> {
|
|
/// Removes heap elements in heap order.
|
|
fn drop(&mut self) {
|
|
struct DropGuard<'r, 'a, T: Ord, A: Allocator + 'a>(&'r mut DrainSorted<'a, T, A>);
|
|
|
|
impl<'r, 'a, T: Ord, A: Allocator + 'a> Drop for DropGuard<'r, 'a, T, A> {
|
|
fn drop(&mut self) {
|
|
while self.0.inner.pop().is_some() {}
|
|
}
|
|
}
|
|
|
|
while let Some(item) = self.inner.pop() {
|
|
let guard = DropGuard(self);
|
|
drop(item);
|
|
mem::forget(guard);
|
|
}
|
|
}
|
|
}
|
|
|
|
#[unstable(feature = "binary_heap_drain_sorted", issue = "59278")]
|
|
impl<'a, T: Ord, A: Allocator + 'a> Iterator for DrainSorted<'a, T, A> {
|
|
type Item = T;
|
|
|
|
#[inline]
|
|
fn next(&mut self) -> Option<T> {
|
|
self.inner.pop()
|
|
}
|
|
|
|
#[inline]
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
let exact = self.inner.len();
|
|
(exact, Some(exact))
|
|
}
|
|
}
|
|
|
|
#[unstable(feature = "binary_heap_drain_sorted", issue = "59278")]
|
|
impl<'a, T: Ord, A: Allocator + 'a> ExactSizeIterator for DrainSorted<'a, T, A> {}
|
|
|
|
#[unstable(feature = "binary_heap_drain_sorted", issue = "59278")]
|
|
impl<'a, T: Ord, A: Allocator + 'a> FusedIterator for DrainSorted<'a, T, A> {}
|
|
|
|
#[unstable(feature = "trusted_len", issue = "37572")]
|
|
unsafe impl<'a, T: Ord, A: Allocator + 'a> TrustedLen for DrainSorted<'a, T, A> {}
|
|
|
|
#[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
|
|
impl<T: Ord, A: Allocator> From<Vec<T, A>> for BinaryHeap<T, A> {
|
|
/// Converts a `Vec<T>` into a `BinaryHeap<T>`.
|
|
///
|
|
/// This conversion happens in-place, and has *O*(*n*) time complexity.
|
|
fn from(vec: Vec<T, A>) -> BinaryHeap<T, A> {
|
|
let mut heap = BinaryHeap { data: vec };
|
|
heap.rebuild();
|
|
heap
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "std_collections_from_array", since = "1.56.0")]
|
|
impl<T: Ord, const N: usize> From<[T; N]> for BinaryHeap<T> {
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
///
|
|
/// let mut h1 = BinaryHeap::from([1, 4, 2, 3]);
|
|
/// let mut h2: BinaryHeap<_> = [1, 4, 2, 3].into();
|
|
/// while let Some((a, b)) = h1.pop().zip(h2.pop()) {
|
|
/// assert_eq!(a, b);
|
|
/// }
|
|
/// ```
|
|
fn from(arr: [T; N]) -> Self {
|
|
Self::from_iter(arr)
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
|
|
impl<T, A: Allocator> From<BinaryHeap<T, A>> for Vec<T, A> {
|
|
/// Converts a `BinaryHeap<T>` into a `Vec<T>`.
|
|
///
|
|
/// This conversion requires no data movement or allocation, and has
|
|
/// constant time complexity.
|
|
fn from(heap: BinaryHeap<T, A>) -> Vec<T, A> {
|
|
heap.data
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T: Ord> FromIterator<T> for BinaryHeap<T> {
|
|
fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> BinaryHeap<T> {
|
|
BinaryHeap::from(iter.into_iter().collect::<Vec<_>>())
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T, A: Allocator> IntoIterator for BinaryHeap<T, A> {
|
|
type Item = T;
|
|
type IntoIter = IntoIter<T, A>;
|
|
|
|
/// Creates a consuming iterator, that is, one that moves each value out of
|
|
/// the binary heap in arbitrary order. The binary heap cannot be used
|
|
/// after calling this.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// Basic usage:
|
|
///
|
|
/// ```
|
|
/// use std::collections::BinaryHeap;
|
|
/// let heap = BinaryHeap::from([1, 2, 3, 4]);
|
|
///
|
|
/// // Print 1, 2, 3, 4 in arbitrary order
|
|
/// for x in heap.into_iter() {
|
|
/// // x has type i32, not &i32
|
|
/// println!("{x}");
|
|
/// }
|
|
/// ```
|
|
fn into_iter(self) -> IntoIter<T, A> {
|
|
IntoIter { iter: self.data.into_iter() }
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<'a, T, A: Allocator + 'a> IntoIterator for &'a BinaryHeap<T, A> {
|
|
type Item = &'a T;
|
|
type IntoIter = Iter<'a, T>;
|
|
|
|
fn into_iter(self) -> Iter<'a, T> {
|
|
self.iter()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
impl<T: Ord, A: Allocator> Extend<T> for BinaryHeap<T, A> {
|
|
#[inline]
|
|
fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
|
|
let guard = RebuildOnDrop { rebuild_from: self.len(), heap: self };
|
|
guard.heap.data.extend(iter);
|
|
}
|
|
|
|
#[inline]
|
|
fn extend_one(&mut self, item: T) {
|
|
self.push(item);
|
|
}
|
|
|
|
#[inline]
|
|
fn extend_reserve(&mut self, additional: usize) {
|
|
self.reserve(additional);
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "extend_ref", since = "1.2.0")]
|
|
impl<'a, T: 'a + Ord + Copy, A: Allocator> Extend<&'a T> for BinaryHeap<T, A> {
|
|
fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
|
|
self.extend(iter.into_iter().cloned());
|
|
}
|
|
|
|
#[inline]
|
|
fn extend_one(&mut self, &item: &'a T) {
|
|
self.push(item);
|
|
}
|
|
|
|
#[inline]
|
|
fn extend_reserve(&mut self, additional: usize) {
|
|
self.reserve(additional);
|
|
}
|
|
}
|