g0201_0300.s0258_add_digits.readme.md Maven / Gradle / Ivy
258\. Add Digits
Easy
Given an integer `num`, repeatedly add all its digits until the result has only one digit, and return it.
**Example 1:**
**Input:** num = 38
**Output:** 2
**Explanation:**
    The process is
    38 --> 3 + 8 --> 11
    11 --> 1 + 1 --> 2
    Since 2 has only one digit, return it. 
**Example 2:**
**Input:** num = 0
**Output:** 0 
**Constraints:**
*   0 <= num <= 231 - 1
**Follow up:** Could you do it without any loop/recursion in `O(1)` runtime?    © 2015 - 2025 Weber Informatics LLC | Privacy Policy