Java对数组实现选择排序算法的实例详解

 public class SelectionSort {   public static void main(String[] args) {     int len = 15;     int[] ary = new int[len];     Random random = new Random();     for (int j = 0; j < len; j++) {       ary[j] = random.nextInt(1000);     }     System.out.println("-------排序前------"); //   ary=new int[]{10,9,8,7,6,5,4,3,2,1}; //测试交换次数 //   ary=new int[]{1,2,3,4,5,6,7,8,10,9}; //测试交换次数     for (int j = 0; j < ary.length; j++) {       System.out.print(ary[j] + " ");     }          selectDesc(ary);     selectAsc(ary);   }   /*    * 选择排序：降序    */   static void selectDesc(int[] ary) {     int compareCount = 0;//比较次数     int changeCount = 0;//交换次数     int len = ary.length;     int maxValueIndex = -1; //记录一轮比较下来的最小值索引     for (int i = 0; i < len - 1; i++) {       maxValueIndex = i; //从0开始       for (int j = i + 1; j < len; j++) {         if (ary[maxValueIndex] < ary[j]) {           maxValueIndex = j; //记录较大的索引           compareCount++;         }       } //     System.out.println("minValueIndex==" + maxValueIndex);       if (maxValueIndex != i) {//如果跟左边的记录索引不同，则交换         ary[i] = ary[maxValueIndex] + (ary[maxValueIndex] = ary[i]) * 0;//一步交换         changeCount++;       }     }          System.out.println("/n-------降序排序后------比较次数：" + compareCount + "，交换次数" + changeCount);     for (int j = 0; j < ary.length; j++) {       System.out.print(ary[j] + " ");     }   }      /*    * 选择排序：升序    */   static void selectAsc(int[] ary) {     int compareCount = 0, changeCount = 0;     int len = ary.length;     int minIndex = -1;     for (int i = 0; i < len - 1; i++) {       minIndex = i;       for (int j = i + 1; j < len; j++) {         if (ary[minIndex] > ary[j]) {           minIndex = j; //记录较小的索引           compareCount++;         }       }       if (minIndex != i) {//如果跟左边的记录索引不同，则交换         ary[i] = ary[minIndex] + (ary[minIndex] = ary[i]) * 0;         changeCount++;       }     }     System.out.println("/n-------升序排序后------比较次数：" + compareCount + "，交换次数" + changeCount);     for (int j = 0; j < ary.length; j++) {       System.out.print(ary[j] + " ");     }   } } 

-------排序前------ 125 350 648 789 319 699 855 755 552 489 187 916 596 731 852  -------降序排序后------比较次数：26，交换次数13 916 855 852 789 755 731 699 648 596 552 489 350 319 187 125  -------升序排序后------比较次数：56，交换次数7 125 187 319 350 489 552 596 648 699 731 755 789 852 855 916