sky_add_digits

很粗暴的解决方式，虽然题目中提到不要用循环，而且要求算法为 O（1），看别人写的代码，觉得很神奇

#include <iostream>using namespace std;class Solution {public:    int addDigits(int num) {        int sum=0;         while(num>0)            {                sum=sum+num%10;                num=num/10;            }           // cout<<"iiii "<<sum<<endl;        while(sum>=10)        {            num=sum;            sum=0;            while(num>0)            {                sum=sum+num%10;                num=num/10;            }           // cout<<"iiii "<<sum%10<<endl;        }        return sum;    }};int main(){   // cout << "Hello world!" << endl;   int num;   cin>>num;   Solution s;   //cout<<num<<endl;   cout<<s.addDigits(num)<<endl;;    return 0;}