Tags: "leetcode", "python", access_time 1-min read

Add Digits

Created: September 23, 2018 by [lek-tin]

Last updated: September 23, 2018

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?

Credits: Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

Explanation

Solution

class Solution {
public:
    int addDigits(int num) {
        return num == 0 ? 0 : (num % 9 == 0 ? 9 : num % 9);
    }
};