题目链接：https://leetcode-cn.com/problems/sort-colors/
题目如下：

class Solution {
public:
    void sortColors(vector<int>& nums) {
        quicksort(nums,0,nums.size()-1);
    }
    void quicksort(vector<int>& nums,int l,int r){
        if(l>=r) return;
        int i=l-1,j=r+1;
        int target=nums[(i+j)>>1];

        while(i<j){
            do i++; while(nums[i]<target);
            do j--; while(nums[j]>target);
            if(i<j) swap(nums[i],nums[j]);
        }

        quicksort(nums,l,j);
        quicksort(nums,j+1,r);
    }
};