Today I have done leetcode's April LeetCoding Challenge with cpp.

April LeetCoding Challenge 26

Description

Add Digits

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?

Solution

class Solution {
public:
  int addDigits(int num) {
    if(!num) return num;
    if(!(num % 9)) return 9;
    return num % 9;
  }
};

// Accepted
// 1101/1101 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 7.98 % of cpp submissions (6 MB)