Skip to main content

Add Digits

Problem statement​

Given an integer num, repeatedly add all its digits until the result has only one digit, and return it.

Example 1:

Input: num = 38Output: 2Explanation: The process is38 --> 3 + 8 --> 1111 --> 1 + 1 --> 2 Since 2 has only one digit, return it.

Example 2:

Input: num = 0Output: 0

Constraints:

  • 0 <= num <= 231 - 1

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

My solution​

/**
 * @param {number} num
 * @return {number}
 */
var addDigits = function(num) {
    if (num === 0) {
        return 0
    }
    
    if (num % 9 === 0) {
        return 9
    }
    return num % 9
};