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    1. /**
    2.  * 快速排序法
    3.  * 6,1,2,7,9,11,4,5,10,8
    4.  * i=4,j=4,arr is 4,1,2,5,6,11,9,7,10,8
    5.  * i=2,j=2,arr is 2,1,4,5,6,11,9,7,10,8
    6.  * i=1,j=1,arr is 1,2,4,5,6,11,9,7,10,8
    7.  * i=0,j=0,arr is 1,2,4,5,6,11,9,7,10,8
    8.  * i=3,j=3,arr is 1,2,4,5,6,11,9,7,10,8
    9.  * i=9,j=9,arr is 1,2,4,5,6,8,9,7,10,11
    10.  * i=6,j=6,arr is 1,2,4,5,6,7,8,9,10,11
    11.  * i=5,j=5,arr is 1,2,4,5,6,7,8,9,10,11
    12.  * i=7,j=7,arr is 1,2,4,5,6,7,8,9,10,11
    13.  * i=8,j=8,arr is 1,2,4,5,6,7,8,9,10,11
    14.  * 1,2,4,5,6,7,8,9,10,11
    15.  * 2022/2/7 18:21
    16.  */
    17. public class Demo1 {
    18.     public static void quickSort(int[] arr, int begin, int end) {
    19.         // 边界
    20.         if (begin > end)
    21.             return;
    23.         // 初始值：以第一个为基准值
    24.         int base = arr[begin];
    25.         int i = begin;
    26.         int j = end;
    27.         while (i != j) {
    28.             while (arr[j] >= base && j > i) {
    29.                 j--;
    30.             }
    31.             while (arr[i] <= base && j > i) {
    32.                 i++;
    33.             }
    34.             if (j > i) {
    35.                 // 当右边的值比基准值小，左边的值比基准值大
    36.                 int t = arr[i];
    37.                 arr[i] = arr[j];
    38.                 arr[j] = t;
    39.             }
    40.         }
    41.         // 交换基准值
    42.         arr[begin] = arr[i];
    43.         arr[i] = base;
    44.         System.out.println("i=" + i + ",j=" + j + ",arr is " + toString(arr));
    45.         // 递归左边
    46.         quickSort(arr, begin, i - 1);
    47.         // 递归右边
    48.         quickSort(arr, i + 1, end);
    49.     }
    51.     public static void main(String[] args) {
    52.         int[] ints = {6, 1, 2, 7, 9, 11, 4, 5, 10, 8};
    53.         System.out.println(toString(ints));
    54.         quickSort(ints, 0, 9);
    55.         System.out.println(toString(ints));
    56.     }
    58.     public static String toString(int[] ints) {
    59.         StringBuilder sb = new StringBuilder();
    60.         for (int i = 0; i < ints.length; i++) {
    61.             sb.append(ints[i]);
    62.             if (i < ints.length - 1) {
    63.                 sb.append(",");
    64.             }
    65.         }
    66.         return sb.toString();
    67.     }
    68. }

    参考博客： https://blog.csdn.net/qq_40941722/article/details/94396010