moved collections from libextra into libcollections

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);
+        }
+    }
+}