单指针快速排序

public class QuickSortTest {public static void main(String[] args) {int[] arr = {2,1,6,1,4};
    quickSort(arr, 0, arr.length - 1);
    print(arr);
  }

  private static void print(int[] arr) {for (int i = 0; i < arr.length; i++) {System.out.print(arr[i] + " ");
    }
  }

  private static void quickSort(int[] arr, int p, int r) {if (p < r) {int q = partition(arr, p, r);
      quickSort(arr, p, q - 1);
      quickSort(arr, q + 1, r);
    }
  }

  private static int partition(int[] arr, int pivot, int r) {
    int p = pivot + 1;
    int bigger = r;
    while (p <= bigger) {if (arr[p] <= arr[pivot]) {p++;} else {swap(arr, p, bigger);
        bigger--;
      }
    }
    // 最后还要一次交换
    swap(arr, pivot, bigger);
    return bigger;
  }

  private static void swap(int[] arr, int p, int bigger) {
    // 交换元素
    int t = arr[p];
    arr[p] = arr[bigger];
    arr[bigger] = t;
  }
}