|
| 1 | +/* |
| 2 | +* Build a max heap out of the array. A heap is a specialized tree like |
| 3 | +* data structure that satisfies the heap property. The heap property |
| 4 | +* for max heap is the following: "if P is a parent node of C, then the |
| 5 | +* key (the value) of node P is greater than the key of node C" |
| 6 | +* Source: https://en.wikipedia.org/wiki/Heap_(data_structure) |
| 7 | +*/ |
| 8 | +Array.prototype.heapify = function (index, heapSize) { |
| 9 | + |
| 10 | + var largest = index; |
| 11 | + var leftIndex = 2 * index + 1; |
| 12 | + var rightIndex = 2 * index + 2; |
| 13 | + |
| 14 | + if (leftIndex < heapSize && this[leftIndex] > this[largest]) { |
| 15 | + largest = leftIndex; |
| 16 | + } |
| 17 | + |
| 18 | + if (rightIndex < heapSize && this[rightIndex] > this[largest]) { |
| 19 | + largest = rightIndex; |
| 20 | + } |
| 21 | + |
| 22 | + if (largest !== index) { |
| 23 | + var temp = this[largest]; |
| 24 | + this[largest] = this[index]; |
| 25 | + this[index] = temp; |
| 26 | + |
| 27 | + this.heapify(largest, heapSize); |
| 28 | + } |
| 29 | +}; |
| 30 | + |
| 31 | +/* |
| 32 | +* Heap sort sorts an array by building a heap from the array and |
| 33 | +* utilizing the heap property. |
| 34 | +* For more information see: https://en.wikipedia.org/wiki/Heapsort |
| 35 | +*/ |
| 36 | +function heapSort(items) { |
| 37 | + |
| 38 | + var length = items.length; |
| 39 | + |
| 40 | + for (var i = Math.floor(items.length / 2) - 1; i > -1; i--) { |
| 41 | + items.heapify(i, length); |
| 42 | + } |
| 43 | + for (var j = length -1; j > 0; j--) { |
| 44 | + var tmp = items[0]; |
| 45 | + items[0] = items[j]; |
| 46 | + items[j] = tmp; |
| 47 | + items.heapify(0, j); |
| 48 | + } |
| 49 | + return items; |
| 50 | +} |
| 51 | + |
| 52 | +//Implementation of heapSort |
| 53 | + |
| 54 | +var ar = [5, 6, 7, 8, 1, 2, 12, 14]; |
| 55 | +//Array before Sort |
| 56 | +console.log(ar); |
| 57 | +heapSort(ar); |
| 58 | +//Array after sort |
| 59 | +console.log(ar); |
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