# https://leetcode.com/problems/merge-strings-alternately/description/
"""
You are given two strings word1 and word2. Merge the strings by adding letters in alternating order, starting with word1. If a string is longer than the other, append the additional letters onto the end of the merged string.

Return the merged string.

Example 1:
Input: word1 = "abc", word2 = "pqr"
Output: "apbqcr"
Explanation: The merged string will be merged as so:
word1:  a   b   c
word2:    p   q   r
merged: a p b q c r

Example 2:
Input: word1 = "ab", word2 = "pqrs"
Output: "apbqrs"
Explanation: Notice that as word2 is longer, "rs" is appended to the end.
word1:  a   b
word2:    p   q   r   s
merged: a p b q   r   s

Example 3:
Input: word1 = "abcd", word2 = "pq"
Output: "apbqcd"
Explanation: Notice that as word1 is longer, "cd" is appended to the end.
word1:  a   b   c   d
word2:    p   q
merged: a p b q c   d

Constraints:
1 <= word1.length, word2.length <= 100
word1 and word2 consist of lowercase English letters.
"""


from itertools import zip_longest


def merge_alternately(word1: str, word2: str) -> str:
    n1, n2 = len(word1), len(word2)
    i, j = 0, 0
    ret = ""
    while i < n1 and j < n2:
        ret += word1[i] + word2[j]
        i += 1
        j += 1
    ret += word1[i:]
    ret += word2[j:]
    return ret


def merge_alternately(word1: str, word2: str) -> str:
    return "".join([a + b for a, b in zip_longest(word1, word2, fillvalue="")])
