题解 | The Biggest Water Problem

#include <stdio.h>
void judge(long long n)
{
    long long a, sum=0;
    while (n)
    {
        a = n % 10;
        n = n / 10;
        sum += a;
    }
    if (sum < 10)//递归判断条件
    {
        printf("%lld", sum);
    }
    else
    {
        judge(sum);
    }
}
int main()
{
    long long n;
    scanf("%lld", &n);
    judge(n);
    return 0;
}