（一）求 int 型数据在内存中存储时 1 的个数

 1 #include <stdio.h>
 2 
 3 int GetCount(int num)
 4 {
 5     /* 功能实现 */
 6     int ret = 0;
 7 
 8     while (num)
 9     {
10         num &= (num - 1);
11         ret++;
12     }
13 
14     return ret;
15 }
16 
17 int main()
18 {
19     int num;
20     int ret;
21 
22     printf_s("Please input a num:");
23     scanf_s("%d", &num);
24 
25     ret = GetCount(num);
26     printf("The number of one is %d\n", ret);
27     return 0;
28 }