题目链接：https://leetcode.cn/problems/permutations/

思路：

只用题目给的nums数组进行递归，swap进行交换，注意还原现场

class Solution {
public:
    vector<vector<int>> permute(vector<int>& nums) {
            vector<vector<int>>ans;
            f(nums,ans,0);
            return ans;
    }
    void f(vector<int>nums,vector<vector<int>>&ans,int i)
    {
        if(i==nums.size())
        {
            ans.push_back(nums);
            return;
        }
        for(int j=i;j<nums.size();j++)
        {
            swap(nums[i],nums[j]);
            f(nums,ans,i+1);
            swap(nums[i],nums[j]);
        }
    }
};