Java版堆排序[不稳定]

堆一般指二叉堆。

复杂度：O(nlogn) - O(nlgn) - O(nlgn) - O(1)[平均 - 最好 - 最坏 - 空间复杂度]

大顶堆实现从小到大的升序排列，小顶堆一般用于构造优先队列

public void heapSort(int[] a) {if (null == a || a.length < 2) {return;}buildMaxHeap(a);for (int i = a.length - 1; i >= 0; i--) {int temp = a[0];a[0] = a[i];a[i] = temp;adjustHeap(a, i, 0);}}// 建堆private void buildMaxHeap(int[] a) {int mid = a.length / 2;for (int i = mid; i >= 0; i--) {adjustHeap(a, a.length, i);}}// 递归调整堆private void adjustHeap(int[] a, int size, int parent) {int left = 2 * parent + 1;int right = 2 * parent + 2;int largest = parent;if (left < size && a[left] > a[parent]) {largest = left;}if (right < size && a[right] > a[largest]) {largest = right;}if (parent != largest) {int temp = a[parent];a[parent] = a[largest];a[largest] = temp;adjustHeap(a, size, largest);}}