剑指offer——16二进制中1的个数

 1 class Solution01 {
 2 public:
 3     int  NumberOf1(int n) {
 4         int cnt = 0;
 5         while (n)
 6         {
 7             if (n & 1)cnt++;
 8             n = n >> 1;
 9         }
10         return cnt;
11     }
12 };

 1 class Solution02 {
 2 public:
 3     int  NumberOf1(int n) {
 4         int cnt = 0;
 5         unsigned num = 1;//一定是无符号的！！！
 6         while (num)
 7         {
 8             if (n & num)cnt++;
 9             num = num << 1;//num<<1不能改变num的
10         }
11         return cnt;
12     }
13 };

 1 class Solution03 {
 2 public:
 3     int  NumberOf1(int n) {
 4         int cnt = 0;
 5         while (n)
 6         {
 7             ++cnt;
 8             n = (n - 1)&n;
 9         }
10         return cnt;
11     }
12 };