subsets（C++实现）

Given a set of distinct integers, 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 = [1,2,3], a solution is:

[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

 

class Solution {
public:
    vector<vector<int> > subsets(vector<int> &S) {
        vector<vector<int> > ret;
        if(S.size() == 0) return ret;
        sort(S.begin(), S.end());
        vector<int> tmp;
        dfs(S, 0, tmp, ret);
        return ret;
    }
    
    void dfs(vector<int> &S, int beg, vector<int> tmp, vector<vector<int> > &ret) {
        ret.push_back(tmp);
        if(beg >= S.size()) return;
        for(int i = beg; i < S.size(); ++i) {
            tmp.push_back(S[i]);
            dfs(S, i+1, tmp, ret);
            tmp.pop_back();
        }
    }
};

 

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