#include
 
int DigitSum(unsigned int n)   
{
    int num = 0;
    if( n == 0)
    {
        return num;
    }
    else
    num = n%10;
    n /= 10;
    return num + DigitSum(n);
}
 
int main()
{
        unsigned int n = 0;
    int ret = 0;
    printf("请输入一个非负整数：");
    scanf("%d",&n);
    ret = DigitSum(n);
    printf("%d\n",ret);
    return 0;
}

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