/
priority_queue.rs
388 lines (335 loc) · 11.3 KB
/
priority_queue.rs
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// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! A priority queue implemented with a binary heap
#[allow(missing_doc)];
use std::clone::Clone;
use std::unstable::intrinsics::{move_val_init, init};
use std::util::{replace, swap};
use std::vec;
/// A priority queue implemented with a binary heap
#[deriving(Clone)]
pub struct PriorityQueue<T> {
priv data: ~[T],
}
impl<T:Ord> Container for PriorityQueue<T> {
/// Returns the length of the queue
fn len(&self) -> uint { self.data.len() }
}
impl<T:Ord> Mutable for PriorityQueue<T> {
/// Drop all items from the queue
fn clear(&mut self) { self.data.truncate(0) }
}
impl<T:Ord> PriorityQueue<T> {
/// An iterator visiting all values in underlying vector, in
/// arbitrary order.
pub fn iter<'a>(&'a self) -> Items<'a, T> {
Items { iter: self.data.iter() }
}
/// Returns the greatest item in the queue - fails if empty
pub fn top<'a>(&'a self) -> &'a T { &self.data[0] }
/// Returns the greatest item in the queue - None if empty
pub fn maybe_top<'a>(&'a self) -> Option<&'a T> {
if self.is_empty() { None } else { Some(self.top()) }
}
/// Returns the number of elements the queue can hold without reallocating
pub fn capacity(&self) -> uint { self.data.capacity() }
/// Reserve capacity for exactly n elements in the PriorityQueue.
/// Do nothing if the capacity is already sufficient.
pub fn reserve_exact(&mut self, n: uint) { self.data.reserve_exact(n) }
/// Reserve capacity for at least n elements in the PriorityQueue.
/// Do nothing if the capacity is already sufficient.
pub fn reserve(&mut self, n: uint) {
self.data.reserve(n)
}
/// Pop the greatest item from the queue - fails if empty
pub fn pop(&mut self) -> T {
let mut item = self.data.pop().unwrap();
if !self.is_empty() {
swap(&mut item, &mut self.data[0]);
self.siftdown(0);
}
item
}
/// Pop the greatest item from the queue - None if empty
pub fn maybe_pop(&mut self) -> Option<T> {
if self.is_empty() { None } else { Some(self.pop()) }
}
/// Push an item onto the queue
pub fn push(&mut self, item: T) {
self.data.push(item);
let new_len = self.len() - 1;
self.siftup(0, new_len);
}
/// Optimized version of a push followed by a pop
pub fn push_pop(&mut self, mut item: T) -> T {
if !self.is_empty() && self.data[0] > item {
swap(&mut item, &mut self.data[0]);
self.siftdown(0);
}
item
}
/// Optimized version of a pop followed by a push - fails if empty
pub fn replace(&mut self, mut item: T) -> T {
swap(&mut item, &mut self.data[0]);
self.siftdown(0);
item
}
/// Consume the PriorityQueue and return the underlying vector
pub fn to_vec(self) -> ~[T] { let PriorityQueue{data: v} = self; v }
/// Consume the PriorityQueue and return a vector in sorted
/// (ascending) order
pub fn to_sorted_vec(self) -> ~[T] {
let mut q = self;
let mut end = q.len();
while end > 1 {
end -= 1;
q.data.swap(0, end);
q.siftdown_range(0, end)
}
q.to_vec()
}
/// Create an empty PriorityQueue
pub fn new() -> PriorityQueue<T> { PriorityQueue{data: ~[],} }
/// Create a PriorityQueue from a vector (heapify)
pub fn from_vec(xs: ~[T]) -> PriorityQueue<T> {
let mut q = PriorityQueue{data: xs,};
let mut n = q.len() / 2;
while n > 0 {
n -= 1;
q.siftdown(n)
}
q
}
// The implementations of siftup and siftdown use unsafe blocks in
// order to move an element out of the vector (leaving behind a
// zeroed element), shift along the others and move it back into the
// vector over the junk element. This reduces the constant factor
// compared to using swaps, which involves twice as many moves.
fn siftup(&mut self, start: uint, mut pos: uint) {
unsafe {
let new = replace(&mut self.data[pos], init());
while pos > start {
let parent = (pos - 1) >> 1;
if new > self.data[parent] {
let x = replace(&mut self.data[parent], init());
move_val_init(&mut self.data[pos], x);
pos = parent;
continue
}
break
}
move_val_init(&mut self.data[pos], new);
}
}
fn siftdown_range(&mut self, mut pos: uint, end: uint) {
unsafe {
let start = pos;
let new = replace(&mut self.data[pos], init());
let mut child = 2 * pos + 1;
while child < end {
let right = child + 1;
if right < end && !(self.data[child] > self.data[right]) {
child = right;
}
let x = replace(&mut self.data[child], init());
move_val_init(&mut self.data[pos], x);
pos = child;
child = 2 * pos + 1;
}
move_val_init(&mut self.data[pos], new);
self.siftup(start, pos);
}
}
fn siftdown(&mut self, pos: uint) {
let len = self.len();
self.siftdown_range(pos, len);
}
}
/// PriorityQueue iterator
pub struct Items <'a, T> {
priv iter: vec::Items<'a, T>,
}
impl<'a, T> Iterator<&'a T> for Items<'a, T> {
#[inline]
fn next(&mut self) -> Option<(&'a T)> { self.iter.next() }
#[inline]
fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
}
impl<T: Ord> FromIterator<T> for PriorityQueue<T> {
fn from_iterator<Iter: Iterator<T>>(iter: &mut Iter) -> PriorityQueue<T> {
let mut q = PriorityQueue::new();
q.extend(iter);
q
}
}
impl<T: Ord> Extendable<T> for PriorityQueue<T> {
fn extend<Iter: Iterator<T>>(&mut self, iter: &mut Iter) {
let (lower, _) = iter.size_hint();
let len = self.capacity();
self.reserve(len + lower);
for elem in *iter {
self.push(elem);
}
}
}
#[cfg(test)]
mod tests {
use priority_queue::PriorityQueue;
#[test]
fn test_iterator() {
let data = ~[5, 9, 3];
let iterout = ~[9, 5, 3];
let pq = PriorityQueue::from_vec(data);
let mut i = 0;
for el in pq.iter() {
assert_eq!(*el, iterout[i]);
i += 1;
}
}
#[test]
fn test_top_and_pop() {
let data = ~[2u, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1];
let mut sorted = data.clone();
sorted.sort();
let mut heap = PriorityQueue::from_vec(data);
while !heap.is_empty() {
assert_eq!(heap.top(), sorted.last().unwrap());
assert_eq!(heap.pop(), sorted.pop().unwrap());
}
}
#[test]
fn test_push() {
let mut heap = PriorityQueue::from_vec(~[2, 4, 9]);
assert_eq!(heap.len(), 3);
assert!(*heap.top() == 9);
heap.push(11);
assert_eq!(heap.len(), 4);
assert!(*heap.top() == 11);
heap.push(5);
assert_eq!(heap.len(), 5);
assert!(*heap.top() == 11);
heap.push(27);
assert_eq!(heap.len(), 6);
assert!(*heap.top() == 27);
heap.push(3);
assert_eq!(heap.len(), 7);
assert!(*heap.top() == 27);
heap.push(103);
assert_eq!(heap.len(), 8);
assert!(*heap.top() == 103);
}
#[test]
fn test_push_unique() {
let mut heap = PriorityQueue::from_vec(~[~2, ~4, ~9]);
assert_eq!(heap.len(), 3);
assert!(*heap.top() == ~9);
heap.push(~11);
assert_eq!(heap.len(), 4);
assert!(*heap.top() == ~11);
heap.push(~5);
assert_eq!(heap.len(), 5);
assert!(*heap.top() == ~11);
heap.push(~27);
assert_eq!(heap.len(), 6);
assert!(*heap.top() == ~27);
heap.push(~3);
assert_eq!(heap.len(), 7);
assert!(*heap.top() == ~27);
heap.push(~103);
assert_eq!(heap.len(), 8);
assert!(*heap.top() == ~103);
}
#[test]
fn test_push_pop() {
let mut heap = PriorityQueue::from_vec(~[5, 5, 2, 1, 3]);
assert_eq!(heap.len(), 5);
assert_eq!(heap.push_pop(6), 6);
assert_eq!(heap.len(), 5);
assert_eq!(heap.push_pop(0), 5);
assert_eq!(heap.len(), 5);
assert_eq!(heap.push_pop(4), 5);
assert_eq!(heap.len(), 5);
assert_eq!(heap.push_pop(1), 4);
assert_eq!(heap.len(), 5);
}
#[test]
fn test_replace() {
let mut heap = PriorityQueue::from_vec(~[5, 5, 2, 1, 3]);
assert_eq!(heap.len(), 5);
assert_eq!(heap.replace(6), 5);
assert_eq!(heap.len(), 5);
assert_eq!(heap.replace(0), 6);
assert_eq!(heap.len(), 5);
assert_eq!(heap.replace(4), 5);
assert_eq!(heap.len(), 5);
assert_eq!(heap.replace(1), 4);
assert_eq!(heap.len(), 5);
}
fn check_to_vec(mut data: ~[int]) {
let heap = PriorityQueue::from_vec(data.clone());
let mut v = heap.clone().to_vec();
v.sort();
data.sort();
assert_eq!(v, data);
assert_eq!(heap.to_sorted_vec(), data);
}
#[test]
fn test_to_vec() {
check_to_vec(~[]);
check_to_vec(~[5]);
check_to_vec(~[3, 2]);
check_to_vec(~[2, 3]);
check_to_vec(~[5, 1, 2]);
check_to_vec(~[1, 100, 2, 3]);
check_to_vec(~[1, 3, 5, 7, 9, 2, 4, 6, 8, 0]);
check_to_vec(~[2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1]);
check_to_vec(~[9, 11, 9, 9, 9, 9, 11, 2, 3, 4, 11, 9, 0, 0, 0, 0]);
check_to_vec(~[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
check_to_vec(~[10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0]);
check_to_vec(~[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 0, 0, 1, 2]);
check_to_vec(~[5, 4, 3, 2, 1, 5, 4, 3, 2, 1, 5, 4, 3, 2, 1]);
}
#[test]
#[should_fail]
fn test_empty_pop() {
let mut heap: PriorityQueue<int> = PriorityQueue::new();
heap.pop();
}
#[test]
fn test_empty_maybe_pop() {
let mut heap: PriorityQueue<int> = PriorityQueue::new();
assert!(heap.maybe_pop().is_none());
}
#[test]
#[should_fail]
fn test_empty_top() {
let empty: PriorityQueue<int> = PriorityQueue::new();
empty.top();
}
#[test]
fn test_empty_maybe_top() {
let empty: PriorityQueue<int> = PriorityQueue::new();
assert!(empty.maybe_top().is_none());
}
#[test]
#[should_fail]
fn test_empty_replace() {
let mut heap: PriorityQueue<int> = PriorityQueue::new();
heap.replace(5);
}
#[test]
fn test_from_iter() {
let xs = ~[9u, 8, 7, 6, 5, 4, 3, 2, 1];
let mut q: PriorityQueue<uint> = xs.rev_iter().map(|&x| x).collect();
for &x in xs.iter() {
assert_eq!(q.pop(), x);
}
}
}