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