Subsets

description:

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],
  []
]

slove:

通过位标记来记录某个值是否参与到此次组合。

class Solution {
public:
    vector<vector<int> > subsets(vector<int> &S) {
        vector<vector<int> > ret;
        std::sort(S.begin(), S.end());
        run(ret, S);
        return ret;
    }
    void run(vector<vector<int> >&ret, vector<int> str) {
        vector<int> res;
        ret.push_back(res);
        int len = str.size();
        for(int i = 1; i < (1<<len); ++ i) {
            for(int j = 0; j < len; ++ j) {
                if(i & (1 << j)) {
                    res.push_back(str.at(j));
                }
            }
            ret.push_back(res);
            res.clear();
        }
    }

};


坑：
输入向量不一定是有序的。