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/* $Id$ */
/**
* Priority Queue.
* Peek and Pop always return the current lowest value in the list.
* Sort is done on insertion only.
*/
class PriorityQueue
{
_queue = null;
_count = 0;
constructor()
{
_count = 0;
_queue = [];
}
/**
* Insert a new entry in the list.
* The complexity of this operation is O(n).
* @param item The item to add to the list.
* @param priority The priority this item has.
*/
function Insert(item, priority);
/**
* Pop the first entry of the list.
* This is always the item with the lowest priority.
* The complexity of this operation is O(1).
* @return The item of the entry with the lowest priority.
*/
function Pop();
/**
* Peek the first entry of the list.
* This is always the item with the lowest priority.
* The complexity of this operation is O(1).
* @return The item of the entry with the lowest priority.
*/
function Peek();
/**
* Get the amount of current items in the list.
* The complexity of this operation is O(1).
* @return The amount of items currently in the list.
*/
function Count();
/**
* Check if an item exists in the list.
* The complexity of this operation is O(n).
* @param item The item to check for.
* @return True if the item is already in the list.
*/
function Exists(item);
};
function PriorityQueue::Insert(item, priority)
{
/* Append dummy entry */
_queue.append(0);
_count++;
local i;
/* Find the point of insertion */
for (i = _count - 2; i >= 0; i--) {
if (priority > _queue[i][1]) {
/* All items bigger move one place to the right */
_queue[i + 1] = _queue[i];
} else if (item == _queue[i][0]) {
/* Same item, ignore insertion */
return false;
} else {
/* Found place to insert at */
break;
}
}
/* Insert new pair */
_queue[i + 1] = [item, priority];
return true;
}
function PriorityQueue::Pop()
{
if (_count == 0) return null;
local node = _queue.pop();
_count--;
return node[0];
}
function PriorityQueue::Peek()
{
if (_count == 0) return null;
return _queue[_count - 1][0];
}
function PriorityQueue::Count()
{
return _count;
}
function PriorityQueue::Exists(item)
{
/* Brute-force find the item (there is no faster way, as we don't have the priority number) */
foreach (node in _queue) {
if (node[0] == item) return true;
}
return false;
}
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