Leetcode49: Add Digits

Given a non-negative integer num, repeatedly add all its digits until the result has only one digit.

For example:

Given num = 38, the process is like: 3 + 8 = 11, 1 + 1 = 2. Since 2 has only one digit, return it.

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