class Solution {
public:
    int n;
    vector<vector<int>> ans;
    vector<int> res;
    vector<int> a;
    bool vis[7];
    inline void dfs(int u) {
        if(u > n) {
            ans.push_back(res);
            return ;
        }
        for (int i = 0; i < n; i ++) {
            if(vis[i]) continue;
            vis[i] = true;
            res.push_back(a[i]);
            dfs(u + 1);
            res.pop_back();
            vis[i] = false;
        }
    }
    vector<vector<int>> permute(vector<int>& nums) {
        a = nums;
        n = nums.size();
        dfs(1);
        return ans;
    }
};