剑指offer：二进制中1的个数

 1    public int NumberOf1(int n) {
 2        int count = 0;
 3        int k = 1;
 4        while (k != 0) {
 5            if ((n & k) != 0) {
 6                count++;
 7            }
 8            k = k << 1;
 9        }
10        return count;
11    }

1    public int NumberOf12(int n) {
2        int count = 0;
3        int k = 1;
4        while (n != 0) {
5            count++;
6            n = (n - 1) & n;
7        }
8        return count;
9    }