LeetCode Subsets II

题目：

Given a collection of integers that might contain duplicates, S, return all possible subsets.

Note:

• Elements in a subset must be in non-descending order.
• The solution set must not contain duplicate subsets.

For example,
If S = [1,2,2], a solution is:

[  [2],  [1],  [1,2,2],  [2,2],  [1,2],  []]

class Solution {public:vector<vector<int> > subsetsWithDup(vector<int> &S) {sort(S.begin(), S.end());int n = S.size();vector<int> row;ans.clear();K.clear();dfs(0, row, n, S);ans.insert(ans.begin(), K.begin(), K.end());return ans;}private:vector<vector<int>> ans;set<vector<int>> K;void dfs(int depth, vector<int> row, int n, vector<int> &S) {if (depth == n) {K.insert(row);return;}dfs(depth + 1, row, n, S);row.push_back(S[depth]);dfs(depth + 1, row, n, S);}};