2013-01-18 01:28:42 -06:00
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// 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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2012-12-09 19:02:33 -06:00
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2012-12-16 21:53:24 -06:00
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//! A priority queue implemented with a binary heap
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2013-01-21 20:59:19 -06:00
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use core::container::{Container, Mutable};
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use core::cmp::Ord;
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use core::prelude::*;
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2012-12-23 16:41:37 -06:00
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use core::ptr::addr_of;
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use core::vec;
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2012-12-09 19:02:33 -06:00
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2012-12-15 12:24:10 -06:00
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#[abi = "rust-intrinsic"]
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extern "C" mod rusti {
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fn move_val_init<T>(dst: &mut T, -src: T);
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}
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pub struct PriorityQueue <T: Ord>{
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priv data: ~[T],
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}
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2013-01-21 20:59:19 -06:00
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impl <T: Ord> PriorityQueue<T>: Container {
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/// Returns the length of the queue
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pure fn len(&self) -> uint { self.data.len() }
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/// Returns true if a queue contains no elements
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pure fn is_empty(&self) -> bool { self.data.is_empty() }
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}
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2013-01-21 16:25:57 -06:00
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impl <T: Ord> PriorityQueue<T>: Mutable {
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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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/// Returns the greatest item in the queue - fails if empty
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pure fn top(&self) -> &self/T { &self.data[0] }
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/// Returns the greatest item in the queue - None if empty
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pure fn maybe_top(&self) -> Option<&self/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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pure fn capacity(&self) -> uint { vec::capacity(&self.data) }
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fn reserve(&mut self, n: uint) { vec::reserve(&mut self.data, n) }
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fn reserve_at_least(&mut self, n: uint) {
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vec::reserve_at_least(&mut self.data, n)
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}
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/// Pop the greatest item from the queue - fails if empty
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fn pop(&mut self) -> T {
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let mut item = self.data.pop();
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if !self.is_empty() { item <-> self.data[0]; self.siftdown(0); }
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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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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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fn push(&mut self, item: T) {
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self.data.push(item);
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self.siftup(0, self.len() - 1);
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}
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/// Optimized version of a push followed by a pop
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fn push_pop(&mut self, item: T) -> T {
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let mut item = item;
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if !self.is_empty() && self.data[0] > item {
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item <-> 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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fn replace(&mut self, item: T) -> T {
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let mut item = item;
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item <-> self.data[0];
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self.siftdown(0);
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item
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}
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2012-12-10 14:36:01 -06:00
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/// Consume the PriorityQueue and return the underlying vector
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pure 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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pure 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[end] <-> q.data[0];
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unsafe { q.siftdown_range(0, end) } // purity-checking workaround
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}
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q.to_vec()
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}
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2012-12-17 17:08:59 -06:00
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/// Create an empty PriorityQueue
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static pure fn new() -> PriorityQueue<T> { PriorityQueue{data: ~[],} }
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/// Create a PriorityQueue from a vector (heapify)
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static pure 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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unsafe { q.siftdown(n) }; // purity-checking workaround
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}
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q
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}
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2012-12-16 21:56:09 -06:00
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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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// junk 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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2013-01-23 13:43:58 -06:00
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priv fn siftup(&mut self, start: uint, pos: uint) {
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unsafe {
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let mut pos = pos;
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let new = move *addr_of(&self.data[pos]);
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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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rusti::move_val_init(&mut self.data[pos],
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move *addr_of(&self.data[parent]));
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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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rusti::move_val_init(&mut self.data[pos], move new);
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}
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}
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2013-01-23 13:43:58 -06:00
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priv fn siftdown_range(&mut self, pos: uint, end: uint) {
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unsafe {
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let mut pos = pos;
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let start = pos;
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let new = move *addr_of(&self.data[pos]);
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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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rusti::move_val_init(&mut self.data[pos],
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move *addr_of(&self.data[child]));
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pos = child;
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child = 2 * pos + 1;
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}
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2013-01-23 13:43:58 -06:00
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rusti::move_val_init(&mut self.data[pos], move new);
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self.siftup(start, pos);
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}
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}
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2012-12-11 16:34:50 -06:00
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priv fn siftdown(&mut self, pos: uint) {
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self.siftdown_range(pos, self.len());
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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 core::cmp::le;
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use priority_queue::PriorityQueue::{from_vec, new};
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#[test]
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fn test_top_and_pop() {
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let data = ~[2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1];
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let mut sorted = merge_sort(data, le);
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let mut heap = from_vec(data);
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while !heap.is_empty() {
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assert *heap.top() == sorted.last();
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assert 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 = from_vec(~[2, 4, 9]);
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assert heap.len() == 3;
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assert *heap.top() == 9;
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heap.push(11);
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assert heap.len() == 4;
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assert *heap.top() == 11;
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heap.push(5);
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assert heap.len() == 5;
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assert *heap.top() == 11;
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heap.push(27);
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assert heap.len() == 6;
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assert *heap.top() == 27;
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heap.push(3);
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assert heap.len() == 7;
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assert *heap.top() == 27;
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heap.push(103);
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assert heap.len() == 8;
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assert *heap.top() == 103;
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}
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2012-12-16 21:53:14 -06:00
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#[test]
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fn test_push_unique() {
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let mut heap = from_vec(~[~2, ~4, ~9]);
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assert heap.len() == 3;
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assert *heap.top() == ~9;
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heap.push(~11);
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assert heap.len() == 4;
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assert *heap.top() == ~11;
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heap.push(~5);
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assert heap.len() == 5;
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assert *heap.top() == ~11;
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heap.push(~27);
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assert heap.len() == 6;
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assert *heap.top() == ~27;
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heap.push(~3);
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assert heap.len() == 7;
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assert *heap.top() == ~27;
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heap.push(~103);
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assert 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 = from_vec(~[5, 5, 2, 1, 3]);
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assert heap.len() == 5;
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assert heap.push_pop(6) == 6;
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assert heap.len() == 5;
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assert heap.push_pop(0) == 5;
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assert heap.len() == 5;
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assert heap.push_pop(4) == 5;
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assert heap.len() == 5;
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assert heap.push_pop(1) == 4;
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assert 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 = from_vec(~[5, 5, 2, 1, 3]);
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assert heap.len() == 5;
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assert heap.replace(6) == 5;
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assert heap.len() == 5;
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assert heap.replace(0) == 6;
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assert heap.len() == 5;
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assert heap.replace(4) == 5;
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assert heap.len() == 5;
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assert heap.replace(1) == 4;
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assert heap.len() == 5;
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}
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2012-12-11 09:57:37 -06:00
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fn check_to_vec(data: ~[int]) {
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let heap = from_vec(data);
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assert merge_sort(heap.to_vec(), le) == merge_sort(data, le);
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assert heap.to_sorted_vec() == merge_sort(data, le);
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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 = 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 = 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 = new::<int>(); empty.top(); }
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2012-12-09 19:02:33 -06:00
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#[test]
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fn test_empty_maybe_top() {
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2012-12-17 17:08:59 -06:00
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let empty = new::<int>();
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2012-12-11 11:19:20 -06:00
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assert empty.maybe_top().is_none();
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2012-12-09 19:02:33 -06:00
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}
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#[test]
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#[should_fail]
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2012-12-16 21:41:07 -06:00
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#[ignore(cfg(windows))]
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2012-12-17 17:08:59 -06:00
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fn test_empty_replace() { let mut heap = new(); heap.replace(5); }
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2012-12-09 19:02:33 -06:00
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}
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