[LeedCode OJ]#258 Add Digits

class Solution
{
public:
    int addDigits(int num)
    {
        int sum;
        while(num>9)
        {
            sum = 0;
            while(num)
            {
                sum+=(num%10);
                num/=10;
            }
            num = sum;
        }
        return num;

    }
};