LeetCode: Subsets

Given a set of distinct integers,S, Return all possible subsets.

Note:

Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets.

For example,

IfS=[1,2,3], A solution is:

[[3], [1], [2], [, 3], [], [], [], [], [] solutions: because the number in the S set is different, there must be 2 ^ n subsets. It is estimated that the n value in the background data should not be greater than 32, so we can use the binary value of an integer to indicate whether a number appears in the set and then enumerate it. solution code:
class Solution {public:    vector
  
    > subsets(vector
   
     &S)     {        int n = S.size();        sort(S.begin(),S.end());        vector
    
      > res;        for (int i = 0; i < 1 << n; ++i)        {            vector
     
       vec ;            int tmp = i , cnt = 0 ;            while (tmp)            {                if (tmp & 1)                    vec.push_back(S[cnt]);                tmp >>= 1 , ++cnt ;            }            res.push_back(vector
      
       (vec.begin(),vec.end()));        }        return res;    }};