用C语言用循环写大佬求解

答案如下： 

#include "stdio.h"

void main()
{
    int num;
    printf("please input a num \n");
    scanf_s("%d", &num);

    int sum = 0;
    while (num)
    {
        sum += num % 10;
        num /= 10;
    }
    printf("sumarry is:%d", sum);
}