快速排序对称模板

记住对称性，记住双swap

class Solution {
public:
    vector<int> sortArray(vector<int>& nums) {
        sort(nums,0,nums.size()-1);
        return nums;
    }

    void sort(vector<int>& nums, int start, int end){
        if(start>=end) return;
        int index = rand()%(end-start+1)+start;
        swap(nums[start],nums[index]);
        int key = nums[start], left = start, right = end;
        while(left<right){
            while(left<right&&nums[right]>=key) right--;
            swap(nums[left],nums[right]);
            while(left<right&&nums[left]<=key) left++;
            swap(nums[left],nums[right]);
        }
        sort(nums,start,left-1);
        sort(nums,left+1,end);
    }
};