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],
  []
]

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 Array Backtracking

 

与  1 相同，需考虑重复

class Solution {
private:
    vector<vector<int> > ret;
public:
    void generate(vector<int> vet,vector<int> &S,int i){
        if(i==S.size()){
            for(int k=0;k<ret.size();k++){
                if(vet==ret[k])          //去除重复
                    return;
            }
            ret.push_back(vet);
            return;
        }
        generate(vet,S,i+1);        //相当于取右子树
        vet.push_back(S[i]);             
        generate(vet,S,i+1);       //相当于取左子树
    }
    vector<vector<int> > subsetsWithDup(vector<int> &S) {  
        sort(S.begin(),S.end());
        generate(vector<int>(),S,0);
        return ret;
    }
};