Introduction

In this blog post, we will explore how to solve the LeetCode problem "3403" 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 a string word, and an integer numFriends. Alice is organizing a game for her numFriends friends. There are multiple rounds in the game, where in each round: word is split into numFriends non-empty strings, such that no previous round has had the exact same split. All the split words are put into a box. Find the lexicographically largest string from the box after all the rounds are finished. Example 1: Input: word = "dbca", numFriends = 2 Output: "dbc" Explanation: All possible splits are: "d" and "bca". "db" and "ca". "dbc" and "a". Example 2: Input: word = "gggg", numFriends = 4 Output: "g" Explanation: The only possible split is: "g", "g", "g", and "g". Constraints: 1 <= word.length <= 5 * 103 word consists only of lowercase English letters. 1 <= numFriends <= word.length

Explanation

Here's the breakdown of the solution:

• Identify Possible Splits: Generate all possible ways to split the given word into numFriends non-empty substrings.
• Lexicographical Comparison: Keep track of the lexicographically largest substring encountered so far across all splits.

• Efficient Generation: Optimize split generation to avoid unnecessary computations by iterating through substring lengths and indices appropriately.

• Runtime Complexity: O(n²), where n is the length of the word.

• Storage Complexity: O(n), where n is the length of the word, mainly for storing substrings and the maximum string.

Code

    def largest_split_string(word: str, numFriends: int) -> str:
    """
    Finds the lexicographically largest string from all possible splits of the word into numFriends parts.

    Args:
        word: The input string.
        numFriends: The number of friends (number of splits).

    Returns:
        The lexicographically largest string among all splits.
    """

    n = len(word)
    max_string = ""

    def generate_splits(index: int, current_split: list[str], remaining_friends: int):
        nonlocal max_string

        if remaining_friends == 1:
            current_split.append(word[index:])
            for s in current_split:
                if s > max_string:
                    max_string = s
            current_split.pop()
            return

        for i in range(index + 1, n - remaining_friends + 2):
            current_split.append(word[index:i])
            generate_splits(i, current_split, remaining_friends - 1)
            current_split.pop()

    generate_splits(0, [], numFriends)
    return max_string