原题链接：Leecode 90. 子集 II

DFS

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++)
        {
            if(i>n && nums[i-1]==nums[i] ) continue;
            v.push_back(nums[i]);
            dfs(nums,v,i+1);
            v.pop_back();
        }
    }
    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        sort(nums.begin(),nums.end());
        vector<int> v;
        dfs(nums,v,0);
        return res;
    }
};

位运算

class Solution {
public:
    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        sort(nums.begin(),nums.end());
        vector<vector<int>> res;
        int n=nums.size();
        int len=1<<n;
        for(int i=0;i<len;i++)
        {
            vector<int> v;
            bool flag=true;
            for(int j=0;j<n;j++)
            {
                if((i>>j)&1)
                {
                    if(j>0 && nums[j-1]==nums[j] && !((i>>(j-1))&1))
                    {
                        flag=false;
                        break;
                    }
                    v.push_back(nums[j]);
                }
            }
            if(flag) res.push_back(v);
        }
        return res;
    }
};