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