快速排序採用分治法：
如下圖所示：

public class QuickSort {
    public static void quickSort(int[] a, int low, int high) {
        if (low > high){
            return;
        }
        int start = low;
        int end = high;
        int key = a[low];
        while (low < high){
            while (low <high && a[high] > key){
                high--;
            }
            while (low < high && a[low] <= key){
                low++;
            }
            if(a[low] > a[high]){
                int temp = a[low];
                a[low] = a[high];
                a[high] = temp;
            }
        }
        if(low == high){
            a[start] = a[high];
            a[high] = key;
        }


        if(low > start){
            quickSort(a,start,low-1);
        }
        if(end > low){
            quickSort(a,low+1,end);
        }


    public static void main(String[] args) {
        int[] a = {3, 2, 5, 1, 4, 9, 6, 8, 8, 0, 1};
        System.out.print("排序前：");
        for (int i : a) {
            System.out.print(i);
        }
        System.out.println();
        quickSort(a,0,a.length-1);

        System.out.print("排序後：");
        for (int i : a) {
            System.out.print(i);
        }
        System.out.println();

    }

}