leetcode78.子集

 

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res是序号，res1是实际集合

class Solution {
public:
vector<int> nums1;
vector<int> res,res1;
vector<vector<int>> ans;
void dfs(){
    int i;
    if(res.size()==0){
        ans.push_back(res);
        for(i=0;i<nums1.size();i++){
            res.push_back(i);
            res1.push_back(nums1[i]);
            ans.push_back(res1);
            dfs();
            res1.pop_back();
            res.pop_back();
        }
    }else if(res.size()==nums1.size()){
        return;
    }else{
        for(i=res[res.size()-1]+1;i<nums1.size();i++){
            res.push_back(i);
            res1.push_back(nums1[i]);
            ans.push_back(res1);
            dfs();
            res1.pop_back();
            res.pop_back();
        }
    }
}
    vector<vector<int>> subsets(vector<int>& nums) {
        nums1=nums;
        dfs();
        return ans;
    }
};