题解 | #Digital Roots#（利用goto实现）
Digital Roots
https://www.nowcoder.com/practice/cef727d0af33479c9fb4a9c120702414
#include <iostream>
using namespace std;
int cal(int n){
int root = 0;
if(n < 9) return n;
label: while(n > 0){
root += n % 10;
n = n / 10;
}
if(root > 9){
n = root;
root = 0;
goto label;
}
return root;
}
int main(){
int num;
while(cin >> num){
cout << cal(num) << endl;
}
}
）。