原题链接：Leecode 78. 子集

DFS 1

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

DFS 2

class Solution {
public:
    vector<vector<int>> res;
    vector<int> v;
    void dfs(vector<int>& nums,int n)
    {
        if(n==nums.size())
        {
            res.push_back(v);
            return;
        }
        v.push_back(nums[n]);
        dfs(nums,n+1);
        v.pop_back();
        dfs(nums,n+1);
    }
    vector<vector<int>> subsets(vector<int>& nums) {
        dfs(nums,0);
        return res;
    }
};

位运算

class Solution {
public:
    vector<vector<int>> subsets(vector<int>& nums) {
        vector<vector<int>> res;
        int n=nums.size();
        int len=1<<n;
        for(int i=0;i<len;i++)
        {
            vector<int> v;
            for(int j=0;j<n;j++)
            {
                if(((i>>j)&1)==1)
                {
                    v.push_back(nums[j]);
                }
            }
            res.push_back(v);
        }
        return res;
    }
};