leetcode 258: Add Digits

Add Digits

Total Accepted: 5383 Total Submissions: 11876

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.

Follow up:
Could you do it without any loop/recursion in O(1) runtime?

[思路]

[CODE]

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