代码

#include<stdio.h>
#include<math.h>

int count(int in)
{
    int num=0;
    
    while(in>0)
    {
        num+=in&1;
        in = in>>1;
    }
    
    return num;
}

int main()
{
    int in;
    
    while(scanf("%d", &in) != EOF)
    {
            printf("%d\n", count(in));
    }
}

参考 https://www.nowcoder.com/profile/282085987/codeBookDetail?submissionId=114675403