堆排序

package leetcode.sort;

import java.util.Arrays;
import java.util.Random;

/**
* HeapSort
* Created by blank on 15/8/12.
*/
public class HeapSort {
public static void main(String[] args) {
int[] arr = new int[100000];
for (int i = 0; i < 100000; i++) {
arr[i] = new Random().nextInt(100000000);
}
int[] copy = arr.clone();
heapSort(arr);
Arrays.sort(copy);
for (int i = 0; i < 100000; i++) {
if (arr[i] != copy[i]) {
System.out.println("wrong");
}
}
System.out.println("right");
}

static void heapSort(int[] array) {
if (array == null || array.length <= 1) {
return;
}
for (int i = (array.length - 1) / 2; i >= 0; i--) {
siftDown(array, i, array.length);
}
for (int i = array.length - 1; i >= 0; i--) {
swap(array, i, 0);
siftDown(array, 0, i);
}
}

private static void swap(int[] array, int a, int b) {
if (a >= array.length || b >= array.length) {
return;
}
int tmp = array[a];
array[a] = array[b];
array[b] = tmp;
}

private static void siftDown(int[] array, int root, int hi) {
int half = hi >>> 1;
while (root < half) {
int child = root * 2 + 1;
if (child >= hi) {
return;
}
if (child + 1 < hi && array[child + 1] > array[child]) {
child++;
}
if (array[child] < array[root]) {
return;
}
swap(array, root, child);
root = child;
}
}

}