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79 lines
2.1 KiB
79 lines
2.1 KiB
var Class = require('./Class');
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var swap = require('./swap');
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var isSorted = require('./isSorted');
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exports = Class({
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initialize: function Heap() {
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var cmp =
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arguments.length > 0 && arguments[0] !== undefined
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? arguments[0]
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: isSorted.defComparator;
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this._cmp = cmp;
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this.clear();
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},
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clear: function() {
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this._data = [];
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this.size = 0;
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},
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add: function(item) {
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this._data.push(item);
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this.size++;
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this._heapifyUp(this.size - 1);
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return this.size;
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},
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poll: function() {
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var data = this._data;
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if (this.size > 0) {
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var item = data[0];
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data[0] = data[this.size - 1];
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this.size--;
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this._heapifyDown(0);
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return item;
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}
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},
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peek: function() {
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if (this.size > 0) {
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return this._data[0];
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}
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},
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_heapifyUp: function(idx) {
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var data = this._data;
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var parent = parentIdx(idx);
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while (idx > 0 && this._cmp(data[parent], data[idx]) > 0) {
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swap(data, parent, idx);
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idx = parent;
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parent = parentIdx(idx);
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}
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},
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_heapifyDown: function(idx) {
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var size = this.size;
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var cmp = this._cmp;
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var data = this._data;
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while (leftChildIdx(idx) < size) {
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var smallerIdx = leftChildIdx(idx);
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var rightChild = rightChildIdx(idx);
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if (
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rightChild < size &&
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cmp(data[rightChildIdx], data[smallerIdx]) < 0
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) {
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smallerIdx = rightChild;
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}
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if (cmp(data[idx], data[smallerIdx]) < 0) {
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break;
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} else {
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swap(data, idx, smallerIdx);
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}
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idx = smallerIdx;
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}
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}
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});
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function parentIdx(idx) {
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return Math.floor((idx - 1) / 2);
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}
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function leftChildIdx(idx) {
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return 2 * idx + 1;
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}
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function rightChildIdx(idx) {
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return 2 * idx + 2;
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}
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module.exports = exports;
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