1768. Merge Strings Alternately

https://leetcode.com/problems/merge-strings-alternately/

Python

class Solution:
    def mergeAlternately(self, word1: str, word2: str) -> str:
        result = [] 

        letters1 = list(word1[::-1])
        letters2 = list(word2[::-1])

        is_word1 = True

        while letters1 or letters2:
            if is_word1:
                if letters1:
                    result.append(letters1.pop())
                is_word1 = False
            
            if not is_word1:
                if letters2:
                    result.append(letters2.pop())
                is_word1 = True
        
        return ''.join(result)