题解 | #Digital Roots#

#include<stdio.h>
int DigRoot(int n);
int main() {
    int n;
    scanf("%d", &n);
//  while(scanf("%d",&n)!=EOF)

    printf("%d\n", DigRoot(n));

    return 0;
}
int DigRoot(int n) {
    int sum = 0;
    int t;
    while (n != 0) {
        t = n % 10;
        n = n / 10;
        sum += t;
    }
    if (sum > 0 && sum <= 9)
        return sum;
    else {
        return DigRoot(sum);
    }
}