LeetCode || Permutations

class Solution {public:    void permutation(vector<int>& nums, int start, vector<vector<int>>& permu)    {        if(start == nums.size())        {            permu.push_back(nums);        }                for(int i = start;i<nums.size();i++)        {            //交换i和start,相当于固定start位置的值            int tmp = nums[i];            nums[i] = nums[start];            nums[start] = tmp;                        permutation(nums, start+1, permu);                        //还原之前的交换            tmp = nums[i];            nums[i] = nums[start];            nums[start] = tmp;        }    }    vector<vector<int>> permute(vector<int>& nums) {        vector<vector<int>> permu;        permutation(nums, 0, permu);        return permu;    }};