堆排序

package com.itheima;

import java.util.Arrays;

/**
* 堆排序（也是一种选择排序）
* 包含了两个重要的方法：1.建堆（大顶堆），2.交换堆顶和最后一个元素的值
* @author Administrator
*
*/
public class HeapSort {

/**
 * 堆排序方法的实现
 * @param data
 */
public static void headSort(int a[]){
    System.out.println("开始排序");

    int arrayLength = a.length;

    //循环建立大顶堆
    for (int i = 0; i < a.length - 1; i++) {
        //建堆
        buildMaxHeap(a, a.length - i - 1);
        //交换堆顶和最后一个元素(数组下标从0开始)
        swap(a, 0, arrayLength - i - 1);
        System.out.println(Arrays.toString(a));
    }
}
/**
 * 交换数据
 * @param a
 * @param i
 * @param j
 */
private static void swap(int a[], int i, int j){

    int temp = a[i];
    a[i] = a[j];
    a[j] = temp;

}

/**
 * 对数组data从0到lastIndex建立大顶堆。
 * @param a
 * @param lastIndex
 */
private  static void buildMaxHeap(int data[], int lastIndex){
    //从lastIndex节点处（最后一个节点）的父节点开始:(lastIndex - 1) / 2

    for (int i = (lastIndex - 1) / 2; i >= 0; i--) {
        //k保存正在判断的节点
        int k = i;
        //如果当前k点的子节点存在
        while ((k * 2 + 1) <= lastIndex) {
            // k节点的左子节点的索引
            int biggerIndex = 2 * k + 1;
            //如果biggerIndex<lastIndex，说明biggerIndex + 1 代表的是k节点的右子节点的索引
            if (biggerIndex < lastIndex) {
                // biggerIndex + 1 代表的是k节点的右子节点的索引
                // 如果右子节点的值比较大
                if (data[biggerIndex] < data[biggerIndex + 1]) {
                    //biggerIndex总是记录的是较大子节点的索引
                    biggerIndex ++;

                }

            }
            //如果k节点的值小于其较大子节点的值就叫唤他们
            if (data[k] < data[biggerIndex]) {
                swap(data, k, biggerIndex);
                //将biggerIndex赋给k，重新while进行下一次循环，保证k节点的值大于其左右节点的值
                k = biggerIndex;
            } else {
                break;
            }
        }
    }


}

public static void main(String[] args) {
    // TODO Auto-generated method stub
    int a[] = {49,38,65,97,76,13,27,49,78,34,12,64,5,4,62,99,98,54,56,17,18,23,34,15,35,25,53,51};
    headSort(a);
}

}
运行结果：
开始排序
[4, 98, 65, 97, 76, 64, 62, 49, 78, 34, 34, 35, 53, 51, 27, 49, 38, 54, 56, 17, 18, 23, 12, 15, 13, 25, 5, 99]
[5, 97, 65, 78, 76, 64, 62, 49, 56, 34, 34, 35, 53, 51, 27, 49, 38, 54, 4, 17, 18, 23, 12, 15, 13, 25, 98, 99]
[25, 78, 65, 56, 76, 64, 62, 49, 54, 34, 34, 35, 53, 51, 27, 49, 38, 5, 4, 17, 18, 23, 12, 15, 13, 97, 98, 99]
[13, 76, 65, 56, 34, 64, 62, 49, 54, 25, 34, 35, 53, 51, 27, 49, 38, 5, 4, 17, 18, 23, 12, 15, 78, 97, 98, 99]
[15, 56, 65, 54, 34, 64, 62, 49, 13, 25, 34, 35, 53, 51, 27, 49, 38, 5, 4, 17, 18, 23, 12, 76, 78, 97, 98, 99]
[12, 56, 64, 54, 34, 53, 62, 49, 13, 25, 34, 35, 15, 51, 27, 49, 38, 5, 4, 17, 18, 23, 65, 76, 78, 97, 98, 99]
[23, 56, 62, 54, 34, 53, 51, 49, 13, 25, 34, 35, 15, 12, 27, 49, 38, 5, 4, 17, 18, 64, 65, 76, 78, 97, 98, 99]
[18, 56, 53, 54, 34, 35, 51, 49, 13, 25, 34, 23, 15, 12, 27, 49, 38, 5, 4, 17, 62, 64, 65, 76, 78, 97, 98, 99]
[17, 54, 53, 49, 34, 35, 51, 49, 13, 25, 34, 23, 15, 12, 27, 18, 38, 5, 4, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[4, 49, 53, 49, 34, 35, 51, 38, 13, 25, 34, 23, 15, 12, 27, 18, 17, 5, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[5, 49, 51, 49, 34, 35, 27, 38, 13, 25, 34, 23, 15, 12, 4, 18, 17, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[17, 49, 35, 49, 34, 23, 27, 38, 13, 25, 34, 5, 15, 12, 4, 18, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[17, 49, 35, 38, 34, 23, 27, 18, 13, 25, 34, 5, 15, 12, 4, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[4, 38, 35, 18, 34, 23, 27, 17, 13, 25, 34, 5, 15, 12, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[12, 34, 35, 18, 34, 23, 27, 17, 13, 25, 4, 5, 15, 38, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[15, 34, 27, 18, 34, 23, 12, 17, 13, 25, 4, 5, 35, 38, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[5, 34, 27, 18, 25, 23, 12, 17, 13, 15, 4, 34, 35, 38, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[4, 25, 27, 18, 15, 23, 12, 17, 13, 5, 34, 34, 35, 38, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[5, 25, 23, 18, 15, 4, 12, 17, 13, 27, 34, 34, 35, 38, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[13, 18, 23, 17, 15, 4, 12, 5, 25, 27, 34, 34, 35, 38, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[5, 18, 13, 17, 15, 4, 12, 23, 25, 27, 34, 34, 35, 38, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[12, 17, 13, 5, 15, 4, 18, 23, 25, 27, 34, 34, 35, 38, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[4, 15, 13, 5, 12, 17, 18, 23, 25, 27, 34, 34, 35, 38, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[4, 12, 13, 5, 15, 17, 18, 23, 25, 27, 34, 34, 35, 38, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[5, 12, 4, 13, 15, 17, 18, 23, 25, 27, 34, 34, 35, 38, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[4, 5, 12, 13, 15, 17, 18, 23, 25, 27, 34, 34, 35, 38, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]
[4, 5, 12, 13, 15, 17, 18, 23, 25, 27, 34, 34, 35, 38, 49, 49, 51, 53, 54, 56, 62, 64, 65, 76, 78, 97, 98, 99]