Question

[LeetCode 258] Given a non-negative integer num, repeatedly add all its digits until the result has only one digit.

Submission

Find the digital root of any positive number. The solution appear periodically from 1 to 9.

Java Submission

public class Solution {
    public int addDigits(int num) {
        return (num - 1) % 9 + 1;
    }
}