// Copyright 2006 Google Inc.
// All Rights Reserved.
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// modification, are permitted provided that the following conditions
// are met:
// 
//  * Redistributions of source code must retain the above copyright
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//  * Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in
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/**
 * @fileoverview Datastructure: Priority Queue.
 *
 *
 * This file provides the implementation of a Priority Queue. Smaller priorities
 * move to the front of the queue. If two values have the same priority,
 * it is arbitrary which value will come to the front of the queue first.
 */



goog.provide('goog.structs.PriorityQueue');

goog.require('goog.structs');
goog.require('goog.structs.Heap');


/**
 * Class for Priority Queue datastructure.
 *
 * @constructor
 * @extends {goog.structs.Heap}
 */
goog.structs.PriorityQueue = function() {
  goog.structs.Heap.call(this);
};
goog.inherits(goog.structs.PriorityQueue, goog.structs.Heap);


/**
 * Puts the specified value in the queue.
 * @param {*} priority The priority of the value.
 * @param {*} value The value.
 */
goog.structs.PriorityQueue.prototype.enqueue = function(priority, value) {
  this.insert(priority, value);
};


/**
 * Retrieves and removes the head of this queue.
 * @return {Object|undefined} The element at the head of this queue. Returns
 *     undefined if the queue is empty.
 */
goog.structs.PriorityQueue.prototype.dequeue = function() {
  return this.remove();
};