LeetCode 1768 - 交替合并字符串

class Solution:
    def mergeAlternately(self, word1: str, word2: str) -> str:
        len1, len2 = len(word1), len(word2)
        i, j = 0, 0
        result = ""
        while i < len1 and j < len2:
            result = result + word1[i] + word2[j]
            i += 1
            j += 1
        result += (word1[i:] if i < len1 else word2[j:])
        return result