LeetCode Permutations II

class Solution {

    public:

        vector<vector<int> > permuteUnique(vector<int> &num) {

            vector<vector<int> > result;

            if (num.size() < 1) return result;

            vector<int> path;

            dfs(num, 0, path, result);

        }



        void dfs(vector<int>& dict, int pos, vector<int>& path, vector<vector<int> > &result) {

            int len = dict.size();

            if (pos >= len) {

                result.push_back(path);

                return;

            }

            unordered_set<int> uniques;

            for (int i=pos; i<len; i++) {

                if (i != pos && uniques.count(dict[i]) > 0) continue;

                uniques.insert(dict[i]);

                path.push_back(dict[i]);

                

                int tmp = dict[i];

                dict[i] = dict[pos];

                dict[pos] = tmp;

                

                dfs(dict, pos + 1, path, result);

                path.pop_back();



                tmp = dict[i];

                dict[i] = dict[pos];

                dict[pos] = tmp;

            }

        }

};

 也可以用next_permutation

class Solution {

    public:

    vector<vector<int> > permuteUnique(vector<int> &num) {

            vector<vector<int> > res;

            sort(num.begin(), num.end());

            do {

                res.push_back(num);

            } while (next_permutation(num.begin(), num.end()));

            return res;

        }

        

};