排序算法Java实现——选择排序（堆排序）

/*@(#)ArrayUtils.java   2017-4-22 
 * Copy Right 2017 Bank of Communications Co.Ltd.
 * All Copyright Reserved
 */

package com.sort.cn;

/**
 * TODO Document ArrayUtils
 * <p>
 * @version 1.0.0,2017-4-22
 * @author Singit
 * @since 1.0.0
 */
public class ArrayUtils {
	public static void printArray(int[] array) {  
        System.out.print("{");  
        for (int i = 0; i < array.length; i++) {  
            System.out.print(array[i]);  
            if (i < array.length - 1) {  
                System.out.print(", ");  
            }  
        }  
        System.out.println("}");  
    }  

    public static void exchangeElements(int[] array, int index1, int index2) {  
        int temp = array[index1];  
        array[index1] = array[index2];  
        array[index2] = temp;  
    }  
}

/*@(#)HeapSort.java   2017-4-22 
 * Copy Right 2017 Bank of Communications Co.Ltd.
 * All Copyright Reserved
 */

package com.sort.cn;

/**
 * TODO Document HeapSort
 * <p>
 * @version 1.0.0,2017-4-22
 * @author Singit
 * @since 1.0.0
 */
public class HeapSort {
	public static void main(String[] args) {  
        int[] array = { 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, -1, -2, -3 };  

        System.out.println("Before heap:");  
        ArrayUtils.printArray(array);  

        heapSort(array);  

        System.out.println("After heap sort:");  
        ArrayUtils.printArray(array);  
    }  

    public static void heapSort(int[] array) {  
        if (array == null || array.length <= 1) {  
            return;  
        }  

        buildMaxHeap(array);  

        for (int i = array.length - 1; i >= 1; i--) {  
            ArrayUtils.exchangeElements(array, 0, i);  

            maxHeap(array, i, 0);  
        }  
    }  

    private static void buildMaxHeap(int[] array) {  
        if (array == null || array.length <= 1) {  
            return;  
        }  

        int half = array.length / 2;  
        for (int i = half; i >= 0; i--) {  
            maxHeap(array, array.length, i);  
        }  
    }  

    private static void maxHeap(int[] array, int heapSize, int index) {  
        int left = index * 2 + 1;  
        int right = index * 2 + 2;  

        int largest = index;  
        if (left < heapSize && array[left] > array[index]) {  
            largest = left;  
        }  

        if (right < heapSize && array[right] > array[largest]) {  
            largest = right;  
        }  

        if (index != largest) {  
            ArrayUtils.exchangeElements(array, index, largest);  

            maxHeap(array, heapSize, largest);  
        }  
    }  
}

输出结果：

Before heap:
{9, 8, 7, 6, 5, 4, 3, 2, 1, 0, -1, -2, -3}
After heap sort:
{-3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9}