[LeetCode]Subsets II

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],

  []

]

思考：直接set去重会不会太暴力。。

class Solution {

private:

    vector<vector<int> > res;

    vector<int> ans;

    set<vector<int> > m;

public:

    void DFS(vector<int> S,int n,int start,int dep,int k)

    {

        if(dep==k)

        {

            set<vector<int> >::iterator iter=m.find(ans);

            if(iter==m.end())

            {

                res.push_back(ans);

                m.insert(ans);

            }

            return;

        }

        for(int i=start;i<n-k+1;i++)

        {

            ans.push_back(S[i+dep]);

            DFS(S,n,i,dep+1,k);

            ans.pop_back();

        }

    }

    vector<vector<int> > subsetsWithDup(vector<int> &S) {

        res.clear();

        ans.clear();

        int n=S.size();

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

        for(int k=0;k<=n;k++)

        {

            DFS(S,n,0,0,k);

        }

        return res;

    }

};