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Add Digits

Tags : leetcode, cpp, easy

Problem Statement - link #

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

Examples #

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 #

Solutions #

class Solution {
public:
    int addDigits(int num) {
      return num == 0 ? 0 : 1 + (num - 1) % 9;
    }
};

class Solution {
public:
    int addDigits(int num) {
        int digitalRoot = 0;
        while (num > 0) {
            digitalRoot += num % 10;
            num = num / 10;
            
            if (num == 0 && digitalRoot > 9) {
                num = digitalRoot;
                digitalRoot = 0;  
            }    
        }     
        return digitalRoot;
    }
};