LeetCode258——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.

实现：

class Solution {

public:

    int addDigits(int num) {

        int result = num;

        while (true) {

            if (result < 10) {

                return result;

            }

            num = result;

            result = 0;

            while (num) {

                result = result + num % 10;

                num = num / 10;

            }

        }

    }

};