排序算法Java实现——选择排序（堆排序）

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/*@(#)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}

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