java算法----排序----（7）堆排序

 package log;

 import java.util.Arrays;

 public class Test4 {
     /**
      * 堆排序
      *
      * @param args
      */
     public static void main(String[] args) {
         int arr[] = { 49, 20, 36, 51, 18, 94, 61, 31, 50 };

         // 循环输出该数组内容
         System.out.println("排序之前：");
         for (int a : arr) {
             System.out.print(a + "\t");
         }
         System.out.println();

         int arrlength = arr.length;

         // 循环建堆
         for (int i = 0; i < arrlength - 1; i++) {
             build(arr, arrlength - 1 - i);
             swap(arr, 0, arrlength - 1 - i);
             System.out.println(Arrays.toString(arr));
         }

         // 循环输出该数组内容
         System.out.println("排序之后：");
         for (int a : arr) {
             System.out.print(a + "\t");
         }
         System.out.println();

     }

     private static void build(int[] data, int lastIndex) {
         for (int i = (lastIndex - 1) / 2; i >= 0; i--) {
             int k = i;
             while (k * 2 + 1 <= lastIndex) {
                 int bigIndex = 2 * k + 1;
                 if (bigIndex < lastIndex) {
                     if (data[bigIndex] < data[bigIndex + 1]) {
                         bigIndex++;
                     }
                 }

                 if (data[k] < data[bigIndex]) {
                     swap(data, k, bigIndex);
                     k = bigIndex;
                 } else {
                     break;
                 }

             }
         }
     }

     private static void swap(int[] data, int i, int j) {
         int temp = data[i];
         data[i] = data[j];
         data[j] = temp;
     }

 }

下面是控制台的输出