堆排序
public static void heapSort(int[] arr) {
if (arr == null || arr.length <= 1) {
return;
}
for (int i = arr.length / 2; i >= 0; i--) {
buildHeap(arr, i, arr.length);
}
for (int i = arr.length - 1; i > 0; i--) {
swap(arr, 0, i);
buildHeap(arr, 0, i);
}
}
private static void buildHeap(int[] arr, int i, int n) {
int child;
int father;
for (father = arr[i]; leftChild(i) < n; i = child) {
child = leftChild(i);
if (child != n - 1 && arr[child] < arr[child + 1]) {
child++;
}
if (father < arr[child]) {
arr[i] = arr[child];
} else {
break;
}
}
arr[i] = father;
}
private static int leftChild(int i) {
return 2 * i + 1;
}
private static void swap(int[] arr, int index1, int index2) {
int tmp = arr[index1];
arr[index1] = arr[index2];
arr[index2] = tmp;
}
