Introduction

In this blog post, we will explore how to solve the LeetCode problem "1754" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

You are given two strings word1 and word2. You want to construct a string merge in the following way: while either word1 or word2 are non-empty, choose one of the following options: If word1 is non-empty, append the first character in word1 to merge and delete it from word1. For example, if word1 = "abc" and merge = "dv", then after choosing this operation, word1 = "bc" and merge = "dva". If word2 is non-empty, append the first character in word2 to merge and delete it from word2. For example, if word2 = "abc" and merge = "", then after choosing this operation, word2 = "bc" and merge = "a". Return the lexicographically largest merge you can construct. A string a is lexicographically larger than a string b (of the same length) if in the first position where a and b differ, a has a character strictly larger than the corresponding character in b. For example, "abcd" is lexicographically larger than "abcc" because the first position they differ is at the fourth character, and d is greater than c. Example 1: Input: word1 = "cabaa", word2 = "bcaaa" Output: "cbcabaaaaa" Explanation: One way to get the lexicographically largest merge is: - Take from word1: merge = "c", word1 = "abaa", word2 = "bcaaa" - Take from word2: merge = "cb", word1 = "abaa", word2 = "caaa" - Take from word2: merge = "cbc", word1 = "abaa", word2 = "aaa" - Take from word1: merge = "cbca", word1 = "baa", word2 = "aaa" - Take from word1: merge = "cbcab", word1 = "aa", word2 = "aaa" - Append the remaining 5 a's from word1 and word2 at the end of merge. Example 2: Input: word1 = "abcabc", word2 = "abdcaba" Output: "abdcabcabcaba" Constraints: 1 <= word1.length, word2.length <= 3000 word1 and word2 consist only of lowercase English letters.

Explanation

Here's a breakdown of the approach, followed by the Python code:

• Greedy Approach: At each step, choose the string (word1 or word2) that will lead to the lexicographically larger merge. This involves comparing the suffixes of both strings starting from their current first characters.
• Suffix Comparison: When the first characters of the remaining parts of word1 and word2 are the same, compare the suffixes of word1 and word2 to determine which string to pick from. If the suffixes are equal, prioritize picking from word1 (as per the problem requirement when there is a tie).

• Build the Merge: Append the chosen character to the merge string and remove it from the corresponding word. Repeat until both words are empty.

• Time Complexity: O(mn), where m and n are the lengths of word1 and word2 respectively (due to suffix comparison). *Space Complexity: O(m+n) to store the resulting merged string.

Code

    def largestMerge(word1: str, word2: str) -> str:
    """
    Constructs the lexicographically largest merge of two strings.
    """
    merge = ""
    i = 0
    j = 0
    while i < len(word1) and j < len(word2):
        if word1[i:] > word2[j:]:
            merge += word1[i]
            i += 1
        else:
            merge += word2[j]
            j += 1

    merge += word1[i:]
    merge += word2[j:]
    return merge