Created
January 5, 2015 03:29
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| public class HeapSort { | |
| public static void sort(int[] a) | |
| { | |
| int heapSize = a.length-1; | |
| buildMaxHeap(a, heapSize); | |
| while (heapSize > 0) { | |
| swap(a, 0, heapSize); | |
| heapSize--; | |
| heapify(a, 0, heapSize); | |
| } | |
| } | |
| private static void buildMaxHeap(int[] a, int heapSize) | |
| { | |
| int nonLeaf = (heapSize-1)/2; | |
| for (int i = nonLeaf; i >= 0; i--) { | |
| heapify(a, i, heapSize); | |
| } | |
| } | |
| private static void heapify(int[] a, int i, int heapSize) | |
| { | |
| int left = (2*i) + 1; | |
| int right = (2*i) + 2; | |
| int largest; | |
| if (left <= heapSize && a[left] > a[i]) { | |
| largest = left; | |
| } else { | |
| largest = i; | |
| } | |
| if (right <= heapSize && a[right] > a[largest]) { | |
| largest = right; | |
| } | |
| if (largest != i) { | |
| swap(a, i, largest); | |
| heapify(a, largest, heapSize); | |
| } | |
| } | |
| private static void swap(int[] a, int i, int j) | |
| { | |
| int temp = a[i]; | |
| a[i] = a[j]; | |
| a[j] = temp; | |
| } | |
| } |
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