c++新解法,用bitset容器轻松解决

class Solution {
public:
     int  NumberOf1(int n) {
         bitset<32> a = n;
         int num = 0;
         for (int i = 0; i < 32; i++)
         {
             if (a[i] == 1) num++;
         }
         return num;
     }
};