快速排序(Java实现)

封装成类：

package com.roc.algorithms.sort;

/**
 * 快速排序
 *
 * @author imroc
 */
public class QuickSort {
    public static void sort(int[] a) {
        sort(a, 0, a.length - 1);
    }
    private static void sort(int[] a, int lo, int hi) {
        if (lo >= hi) {
            return;
        }
        int k = partition(a, lo, hi);
        sort(a, lo, k);
        sort(a, k + 1, hi);
    }
    private static int partition(int[] a, int lo, int hi) {
        int i = lo, j = hi + 1;
        while (true) {
            while (a[++i] <= a[lo]) {
                if (i == hi) {
                    break;
                }
            }
            while (a[--j] > a[lo]) {
                if (j == lo) {
                    break;
                }
            }
            if (i >= j) {
                break;
            }
            swap(a, i, j);
        }
        swap(a, lo, j);
        return j;
    }
    private static void swap(int[] a, int i, int j) {
        int t = a[i];
        a[i] = a[j];
        a[j] = t;
    }
}

测试：

int[] a = {9, 0, 6, 5, 8, 2, 1, 7, 4, 3};
System.out.println(Arrays.toString(a));
QuickSort.sort(a);
System.out.println(Arrays.toString(a));

输出：
[9, 0, 6, 5, 8, 2, 1, 7, 4, 3]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]