46 Permutations

// // Created by YUQIONG LI on 19/9/2018. // #include <vector> #include <iostream> using std::vector; using std::cout; using std::endl; class Solution { public: void permuteHelper(vector<int> & nums, vector<int> chosen, vector<vector<int>> & res){ // no more choices to make if (nums.empty()){ if (std::find(res.begin(), res.end(), chosen) == res.end()) res.push_back(chosen); return; } // choose for (int i = 0; i < nums.size(); i++){ int curr = nums[i]; chosen.push_back(curr); nums.erase(nums.begin()+i); // explore permuteHelper(nums, chosen, res); // un-choose chosen.pop_back(); nums.insert(nums.begin()+i, curr); } } vector<vector<int>> permute(vector<int>& nums) { vector<int> chosen; vector<vector<int> > res; permuteHelper(nums, chosen, res); return res; } }; int main(){ vector<int> nums = {1, 2}; Solution s; vector<vector<int>> res = s.permute(nums); for (auto v : res){ std::cout << "Now print one sets of results.\n"; for (int e : v){ std::cout << e << ' '; } std::cout << endl; } return 0; }