剑指office--------二进制中1的个数

 1 class Solution {
 2 public:
 3      int  NumberOf1(int n) {
 4          int ans=0;
 5          int index=1;
 6          while (index!=0){
 7              if (n&index)    ans++;
 8              index<<=1;
 9          }
10          return ans;
11      }
12 };

 1 class Solution {
 2 public:
 3      int  NumberOf1(int n) {
 4          int count=0;
 5          while (n){
 6              count++;
 7              n=(n-1)&n;
 8          }
 9          return count;
10      }
11 };