Classical problem:
1 class Solution { 2 public: 3 void getP(vector<vector<int> > &result, vector<int> &num, vector<int> current, vector<bool> rec) { 4 if (current.size() == num.size()) { 5 result.push_back(current); 6 return; 7 } 8 for (int i = 0; i < num.size(); i++) { 9 if (rec[i]) continue; 10 rec[i] = true; 11 current.push_back(num[i]); 12 getP(result, num, current, rec); 13 rec[i] = false; 14 current.pop_back(); 15 } 16 } 17 vector<vector<int> > permute(vector<int> &num) { 18 vector<vector<int> > result; 19 sort(num.begin(), num.end()); 20 getP(result, num, vector<int> (), vector<bool> (num.size(), false)); 21 return result; 22 } 23 };