LeetCode 078 Subsets

给你一个集合，问有多少个子集。

直接用递归。

class Solution {
public:
    void dfs(int step,int nn,int limit,vector<int>temp,vector<vector<int>>&ans,vector<int>nums){  
        ans.push_back(temp);
        if(step==nn)return ;  
        for(int ii=1;ii<=nn;ii++){  
            if(ii<=limit)continue;  
            if(step+1>temp.size())temp.push_back(nums[ii-1]);  
            else temp[step]=nums[ii-1];  
            dfs(step+1,nn,ii,temp,ans,nums);  
        }  
    }  
    vector<vector<int>> subsets(vector<int>& nums) {
        vector<vector<int>>ans;
        vector<int>temp;
        int len=nums.size();
        sort(nums.begin(),nums.end());
        dfs(0,len,0,temp,ans,nums);
        return ans;
    }
};