leetcode 46. Permutations

Given a collection of distinct numbers, return all possible permutations.

For example,
[1,2,3] have the following permutations:
[1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1].

class Solution {public:vector<vector<int>> permute(vector<int>& nums) {vector<vector<int>>re;if (nums.empty())return re;if (nums.size() == 1){re.push_back(nums);return re;}map<vector<int>, vector<int>>candi;vector<int>aa; candi[aa] = nums;int k = 0;while (true){map<vector<int>, vector<int>>newcandi;for (map<vector<int>, vector<int>>::iterator it = candi.begin(); it != candi.end(); it++){for (int i = 0; i < it->second.size(); i++){vector<int>aa = it->first;aa.push_back(it->second[i]);if (it->second.size() == 2){aa.push_back(it->second[(1 + i) % 2]);re.push_back(aa);}else{vector<int>bb = it->second;bb.erase(bb.begin() + i, bb.begin() + i + 1);newcandi[aa] = bb;}}}if (k == nums.size() - 2)return re;k++;candi = newcandi;}}};

accepted