# UVA 10922 2 the 9s
## 題目連結 [UVA 10922](https://vjudge.net/problem/UVA-10922)
### 題目內容
A well-known trick to know if an integer N is a multiple of nine is to compute the sum S of its digits. If S is a multiple of nine, then so is N. This is a recursive test, and the depth of the recursion needed to obtain the answer on N is called the 9-degree of N. Your job is, given a positive number N, determine if it is a multiple of nine and, if it is, its 9-degree.
### 輸入限制
The input is a file such that each line contains a positive number. A line containing the number 0 is the end of the input. The given numbers can contain up to 1000 digits.
### 輸出限制
The output of the program shall indicate, for each input number, if it is a multiple of nine, and in case it is, the value of its nine-degree. See the sample output for an example of the expected formatting of the output.
### 解題思路
這題要求每位數相加是否為9的倍數，9-degree是要求總共有多少9的倍數
### 程式碼

#include<bits/stdc++.h>
using namespace std;
int main(){
    string n;
    while(cin>>n && n!="0"){
        int cot=0;
        string s=n;
        while(true){
            int ans=0;
            for(int i=0;i<n.length();i++){
                ans+=n[i]-'0';
            }
            if(ans%9==0){
                cot++;
            }
            n=to_string(ans);
            if(n.length()==1){
                break;
            }
        }
        if(cot==0){
            cout<<s<<" is not a multiple of 9."<<endl;
        }
        else{
            cout<<s<<" is a multiple of 9 and has 9-degree "<<cot<<"."<<endl;
        }
    }
}

## 測資
### Sample input
999999999999999999999
9
9999999999999999999999999999998
0
### Sample output
999999999999999999999 is a multiple of 9 and has 9-degree 3.
9 is a multiple of 9 and has 9-degree 1.
9999999999999999999999999999998 is not a multiple of 9.
## 中文題目連結 [zerojudge d672](https://zerojudge.tw/ShowProblem?problemid=d672)