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Diffstat (limited to 'src/libextra/priority_queue.rs')
| -rw-r--r-- | src/libextra/priority_queue.rs | 320 |
1 files changed, 320 insertions, 0 deletions
diff --git a/src/libextra/priority_queue.rs b/src/libextra/priority_queue.rs new file mode 100644 index 00000000000..f1e0027146c --- /dev/null +++ b/src/libextra/priority_queue.rs @@ -0,0 +1,320 @@ +// 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 + +use core::old_iter::BaseIter; +use core::unstable::intrinsics::{move_val_init, init}; +use core::unstable::intrinsics::uninit; +use core::util::{replace, swap}; + +pub struct PriorityQueue<T> { + priv data: ~[T], +} + +impl<T:Ord> BaseIter<T> for PriorityQueue<T> { + /// Visit all values in the underlying vector. + /// + /// The values are **not** visited in order. + fn each(&self, f: &fn(&T) -> bool) -> bool { self.data.each(f) } + + fn size_hint(&self) -> Option<uint> { self.data.size_hint() } +} + +impl<T:Ord> Container for PriorityQueue<T> { + /// Returns the length of the queue + fn len(&const self) -> uint { vec::uniq_len(&const self.data) } + + /// Returns true if a queue contains no elements + fn is_empty(&const self) -> bool { self.len() == 0 } +} + +impl<T:Ord> Mutable for PriorityQueue<T> { + /// Drop all items from the queue + fn clear(&mut self) { self.data.truncate(0) } +} + +pub impl <T:Ord> PriorityQueue<T> { + /// Returns the greatest item in the queue - fails if empty + fn top<'a>(&'a self) -> &'a T { &self.data[0] } + + /// Returns the greatest item in the queue - None if empty + 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 + 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() { + swap(&mut item, &mut 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); + let new_len = self.len() - 1; + self.siftup(0, new_len); + } + + /// Optimized version of a push followed by a pop + 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 + 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 + fn to_vec(self) -> ~[T] { let PriorityQueue{data: v} = self; v } + + /// Consume the PriorityQueue and return a vector in sorted + /// (ascending) order + fn to_sorted_vec(self) -> ~[T] { + let mut q = self; + let mut end = q.len(); + while end > 1 { + end -= 1; + vec::swap(q.data, 0, end); + q.siftdown_range(0, end) + } + q.to_vec() + } + + /// Create an empty PriorityQueue + fn new() -> PriorityQueue<T> { PriorityQueue{data: ~[],} } + + /// Create a PriorityQueue from a vector (heapify) + 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. + + priv 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; + loop + } + break + } + move_val_init(&mut self.data[pos], new); + } + } + + priv 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); + } + } + + priv fn siftdown(&mut self, pos: uint) { + let len = self.len(); + self.siftdown_range(pos, len); + } +} + +#[cfg(test)] +mod tests { + use sort::merge_sort; + use core::cmp::le; + 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_eq!(heap.top(), sorted.last()); + assert_eq!(heap.pop(), sorted.pop()); + } + } + + #[test] + fn test_push() { + let mut heap = 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 = 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 = 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 = 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(data: ~[int]) { + let heap = from_vec(copy data); + assert_eq!(merge_sort((copy heap).to_vec(), le), merge_sort(data, le)); + assert_eq!(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))] + fn test_empty_pop() { let mut heap = new::<int>(); heap.pop(); } + + #[test] + fn test_empty_maybe_pop() { + let mut heap = new::<int>(); + assert!(heap.maybe_pop().is_none()); + } + + #[test] + #[should_fail] + #[ignore(cfg(windows))] + fn test_empty_top() { let empty = new::<int>(); empty.top(); } + + #[test] + fn test_empty_maybe_top() { + let empty = new::<int>(); + assert!(empty.maybe_top().is_none()); + } + + #[test] + #[should_fail] + #[ignore(cfg(windows))] + fn test_empty_replace() { let mut heap = new(); heap.replace(5); } +} |