1768. Merge Strings Alternately

Problem Statement

link: LeetCode.cn LeetCode 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:

Input: word1 = "abc", word2 = "pqr" Output: "apbqcr"

Input: word1 = "ab", word2 = "pqrs" Output: "apbqrs"

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

Solution Approach

Merge characters from both strings alternately and append any remaining characters from the longer string to the result.

Algorithm

1. Iterate through both strings simultaneously: Use a loop to alternate appending characters from word1 and word2 to the result string until reaching the end of the shorter string.
2. Handle remaining characters: After the loop, concatenate the remaining characters from the longer string to the result string.
3. Return the merged string: Construct and return the final merged string by combining the alternated characters and any leftover characters.

Complexity

time complexity: O(n) space complexity: O(n)

Implement

    class Solution:
    def mergeAlternately(self, word1: str, word2: str) -> str:
    l1, l2 = len(word1), len(word2)
    i = 0
    res = ""
    while i < l1 and i < l2:
        res += word1[i]
        res += word2[i]
        i += 1
    res += word1[i:] + word2[i:]
    return res
    

    
    

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