class Solution {
public:
vector<vector<int>> permute(vector<int>& num) {
vector<vector<int>> res;
vector<int> out, visited(num.size(), 0);
permuteDFS(num, 0, visited, out, res);
return res;
}
void permuteDFS(vector<int>& num, int level, vector<int>& visited, vector<int>& out, vector<vector<int>>& res) {
if (level == num.size()) {res.push_back(out); return;}
for (int i = 0; i < num.size(); ++i) {
if (visited[i] == 1) continue;
visited[i] = 1;
out.push_back(num[i]);
permuteDFS(num, level + 1, visited, out, res);
out.pop_back();
visited[i] = 0;
}
}
};