Subsets

题目大意：给定一个数组，要求它的所有子集

解题思路:先对这个数组进行排序，然后用深度遍历

class Solution {public:    vector<vector<int> > subsets(vector<int> &S) {        vector<vector<int> > result;        vector<int> val;        sort(S.begin(), S.end());        subsetsAssist(S, 0, result, val);        return result;    }private:    void subsetsAssist(vector<int> &S, int index, vector<vector<int> > &result, vector<int> &val) {        if(index >= S.size()) {            result.push_back(val);            return;        }        val.push_back(S[index]);        subsetsAssist(S, index + 1, result, val);        val.pop_back();        subsetsAssist(S, index + 1, result, val);    }};