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Diffstat (limited to 'src/libcollections/priority_queue.rs')
| -rw-r--r-- | src/libcollections/priority_queue.rs | 388 |
1 files changed, 388 insertions, 0 deletions
diff --git a/src/libcollections/priority_queue.rs b/src/libcollections/priority_queue.rs new file mode 100644 index 00000000000..3ae3dae9ea3 --- /dev/null +++ b/src/libcollections/priority_queue.rs @@ -0,0 +1,388 @@ +// 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); + } + } +} |