rust/src/libstd/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.
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//! A priority queue implemented with a binary heap
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use core::container::{Container, Mutable};
use core::cmp::Ord;
use core::prelude::*;
use core::ptr::addr_of;
use core::vec;
#[abi = "rust-intrinsic"]
extern "C" mod rusti {
fn move_val_init<T>(dst: &mut T, -src: T);
}
pub struct PriorityQueue <T: Ord>{
priv data: ~[T],
}
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impl <T: Ord> PriorityQueue<T>: Container {
/// Returns the length of the queue
pure fn len(&self) -> uint { self.data.len() }
/// Returns true if a queue contains no elements
pure fn is_empty(&self) -> bool { self.data.is_empty() }
}
impl <T: Ord> PriorityQueue<T>: Mutable {
/// Drop all items from the queue
fn clear(&mut self) { self.data.truncate(0) }
}
impl <T: Ord> PriorityQueue<T> {
/// Returns the greatest item in the queue - fails if empty
pure fn top(&self) -> &self/T { &self.data[0] }
/// Returns the greatest item in the queue - None if empty
pure fn maybe_top(&self) -> Option<&self/T> {
if self.is_empty() { None } else { Some(self.top()) }
}
/// Returns the number of elements the queue can hold without reallocating
pure fn capacity(&self) -> uint { vec::capacity(&self.data) }
fn reserve(&mut self, n: uint) { vec::reserve(&mut self.data, n) }
fn reserve_at_least(&mut self, n: uint) {
vec::reserve_at_least(&mut self.data, n)
}
/// Pop the greatest item from the queue - fails if empty
fn pop(&mut self) -> T {
let mut item = self.data.pop();
if !self.is_empty() { item <-> self.data[0]; self.siftdown(0); }
item
}
/// Pop the greatest item from the queue - None if empty
fn maybe_pop(&mut self) -> Option<T> {
if self.is_empty() { None } else { Some(self.pop()) }
}
/// Push an item onto the queue
fn push(&mut self, item: T) {
self.data.push(item);
self.siftup(0, self.len() - 1);
}
/// Optimized version of a push followed by a pop
fn push_pop(&mut self, item: T) -> T {
let mut item = item;
if !self.is_empty() && self.data[0] > item {
item <-> self.data[0];
self.siftdown(0);
}
item
}
/// Optimized version of a pop followed by a push - fails if empty
fn replace(&mut self, item: T) -> T {
let mut item = item;
item <-> self.data[0];
self.siftdown(0);
item
}
/// Consume the PriorityQueue and return the underlying vector
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
/// (ascending) order
pure fn to_sorted_vec(self) -> ~[T] {
let mut q = self;
let mut end = q.len();
while end > 1 {
end -= 1;
q.data[end] <-> q.data[0];
unsafe { q.siftdown_range(0, end) } // purity-checking workaround
}
q.to_vec()
}
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/// Create an empty PriorityQueue
static pure fn new() -> PriorityQueue<T> { PriorityQueue{data: ~[],} }
/// Create a PriorityQueue from a vector (heapify)
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static pure fn from_vec(xs: ~[T]) -> PriorityQueue<T> {
let mut q = PriorityQueue{data: xs,};
let mut n = q.len() / 2;
while n > 0 {
n -= 1;
unsafe { q.siftdown(n) }; // purity-checking workaround
}
q
}
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// The implementations of siftup and siftdown use unsafe blocks in
// order to move an element out of the vector (leaving behind a
// junk 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.
priv fn siftup(&mut self, start: uint, pos: uint) {
unsafe {
let mut pos = pos;
let new = move *addr_of(&self.data[pos]);
while pos > start {
let parent = (pos - 1) >> 1;
if new > self.data[parent] {
rusti::move_val_init(&mut self.data[pos],
move *addr_of(&self.data[parent]));
pos = parent;
loop
}
break
}
rusti::move_val_init(&mut self.data[pos], move new);
}
}
priv fn siftdown_range(&mut self, pos: uint, end: uint) {
unsafe {
let mut pos = pos;
let start = pos;
let new = move *addr_of(&self.data[pos]);
let mut child = 2 * pos + 1;
while child < end {
let right = child + 1;
if right < end && !(self.data[child] > self.data[right]) {
child = right;
}
rusti::move_val_init(&mut self.data[pos],
move *addr_of(&self.data[child]));
pos = child;
child = 2 * pos + 1;
}
rusti::move_val_init(&mut self.data[pos], move new);
self.siftup(start, pos);
}
}
priv fn siftdown(&mut self, pos: uint) {
self.siftdown_range(pos, self.len());
}
}
#[cfg(test)]
mod tests {
use sort::merge_sort;
use core::cmp::le;
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use priority_queue::PriorityQueue::{from_vec, new};
#[test]
fn test_top_and_pop() {
let data = ~[2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1];
let mut sorted = merge_sort(data, le);
let mut heap = from_vec(data);
while !heap.is_empty() {
assert *heap.top() == sorted.last();
assert heap.pop() == sorted.pop();
}
}
#[test]
fn test_push() {
let mut heap = from_vec(~[2, 4, 9]);
assert heap.len() == 3;
assert *heap.top() == 9;
heap.push(11);
assert heap.len() == 4;
assert *heap.top() == 11;
heap.push(5);
assert heap.len() == 5;
assert *heap.top() == 11;
heap.push(27);
assert heap.len() == 6;
assert *heap.top() == 27;
heap.push(3);
assert heap.len() == 7;
assert *heap.top() == 27;
heap.push(103);
assert heap.len() == 8;
assert *heap.top() == 103;
}
#[test]
fn test_push_unique() {
let mut heap = from_vec(~[~2, ~4, ~9]);
assert heap.len() == 3;
assert *heap.top() == ~9;
heap.push(~11);
assert heap.len() == 4;
assert *heap.top() == ~11;
heap.push(~5);
assert heap.len() == 5;
assert *heap.top() == ~11;
heap.push(~27);
assert heap.len() == 6;
assert *heap.top() == ~27;
heap.push(~3);
assert heap.len() == 7;
assert *heap.top() == ~27;
heap.push(~103);
assert heap.len() == 8;
assert *heap.top() == ~103;
}
#[test]
fn test_push_pop() {
let mut heap = from_vec(~[5, 5, 2, 1, 3]);
assert heap.len() == 5;
assert heap.push_pop(6) == 6;
assert heap.len() == 5;
assert heap.push_pop(0) == 5;
assert heap.len() == 5;
assert heap.push_pop(4) == 5;
assert heap.len() == 5;
assert heap.push_pop(1) == 4;
assert heap.len() == 5;
}
#[test]
fn test_replace() {
let mut heap = from_vec(~[5, 5, 2, 1, 3]);
assert heap.len() == 5;
assert heap.replace(6) == 5;
assert heap.len() == 5;
assert heap.replace(0) == 6;
assert heap.len() == 5;
assert heap.replace(4) == 5;
assert heap.len() == 5;
assert heap.replace(1) == 4;
assert heap.len() == 5;
}
fn check_to_vec(data: ~[int]) {
let heap = from_vec(data);
assert merge_sort(heap.to_vec(), le) == merge_sort(data, le);
assert heap.to_sorted_vec() == merge_sort(data, le);
}
#[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]
#[ignore(cfg(windows))]
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fn test_empty_pop() { let mut heap = new::<int>(); heap.pop(); }
#[test]
fn test_empty_maybe_pop() {
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let mut heap = new::<int>();
assert heap.maybe_pop().is_none();
}
#[test]
#[should_fail]
#[ignore(cfg(windows))]
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fn test_empty_top() { let empty = new::<int>(); empty.top(); }
#[test]
fn test_empty_maybe_top() {
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let empty = new::<int>();
assert empty.maybe_top().is_none();
}
#[test]
#[should_fail]
#[ignore(cfg(windows))]
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fn test_empty_replace() { let mut heap = new(); heap.replace(5); }
}