C语言：用递归函数DigitSum(n)实现输入1729，输出sum=1+7+2+9=19的值

#define _crt_secure_no_warnings
#include<stdio.h>
#include<stdlib.h>
int digitsum(unsigned int num)
{
 int sum = 0;
 int n = 0;
 if (num != 0)
 {
  n = num % 10;
  num = num / 10;
  sum = n + digitsum(num);
 }
 return sum;
}
int main()
{
 unsigned int num = 1729;
 printf("%d\n", digitsum(num));
 system("pause");
 return 0;
}