LeetCode: Merge Strings Alternately

Merge two strings by alternating their characters.

Solution

This solution uses string concatenation with new_word += word1[i]. In Python, strings are immutable, so each += operation creates a new string object. For small-to-medium inputs, this is usually fast enough (and may be optimized in your specific Python implementation). For larger inputs, using a list and ''.join() is more efficient.

class Solution:
    def mergeAlternately(self, word1: str, word2: str) -> str:
        new_word = ""
        len_word1 = len(word1)
        len_word2 = len(word2)
        max_length = max(len_word1, len_word2)
        for i in range(max_length):
            if i < len_word1:
                new_word += word1[i]
            if i < len_word2:
                new_word += word2[i]

        return new_word