Leetcode题解 258. 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.

public static int addDigits(int num) {
        if (num / 10 == 0) {
            return num;
        }
        int result = num;
        Stack<Integer> mStack = new Stack<Integer>();
        while (result / 10 != 0) {
            while (result != 0) {
                mStack.push(result % 10);
                result /= 10;
            }
            while (mStack.size() > 0) {
                result += mStack.pop();
            }
        }
        return result;
    }