快速排序

int middle_partition(int A[],int left,int right)
{
    int middle = A[left];
    while(left<right)
    {
        while(left<right&&A[right]>=middle) right--;
        A[left]=A[right];
        while(left<right&&A[left]<=middle) left++;
        A[right]=A[left];
    }
    A[left]=middle;
    return left;
}

void quick_sort(int a[],int left,int right)
{
    if(left<right)
    {
        int mid=middle_partition(a,left,right);
        quick_sort(a,left,mid-1);
        quick_sort(a,mid+1,right);
    }
}