#include<stdio.h>
int sum = 0;
int DigitSum(int n)
{
if (n>9)
{
DigitSum(n / 10);
}
sum += n % 10;
return sum;
}
int main()
{
int n;
scanf("%d", &n);
printf("%d\n", n);
int sum = DigitSum(n);
printf("%d", sum);
}原文：https://blog.51cto.com/14737345/2479830