Introduction

In this blog post, we will explore how to solve the LeetCode problem "2024" 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

A teacher is writing a test with n true/false questions, with 'T' denoting true and 'F' denoting false. He wants to confuse the students by maximizing the number of consecutive questions with the same answer (multiple trues or multiple falses in a row). You are given a string answerKey, where answerKey[i] is the original answer to the ith question. In addition, you are given an integer k, the maximum number of times you may perform the following operation: Change the answer key for any question to 'T' or 'F' (i.e., set answerKey[i] to 'T' or 'F'). Return the maximum number of consecutive 'T's or 'F's in the answer key after performing the operation at most k times. Example 1: Input: answerKey = "TTFF", k = 2 Output: 4 Explanation: We can replace both the 'F's with 'T's to make answerKey = "TTTT". There are four consecutive 'T's. Example 2: Input: answerKey = "TFFT", k = 1 Output: 3 Explanation: We can replace the first 'T' with an 'F' to make answerKey = "FFFT". Alternatively, we can replace the second 'T' with an 'F' to make answerKey = "TFFF". In both cases, there are three consecutive 'F's. Example 3: Input: answerKey = "TTFTTFTT", k = 1 Output: 5 Explanation: We can replace the first 'F' to make answerKey = "TTTTTFTT" Alternatively, we can replace the second 'F' to make answerKey = "TTFTTTTT". In both cases, there are five consecutive 'T's. Constraints: n == answerKey.length 1 <= n <= 5 * 104 answerKey[i] is either 'T' or 'F' 1 <= k <= n

Explanation

Here's the breakdown of the problem and the optimal solution:

• Sliding Window: The core idea is to use a sliding window approach. We expand the window until the number of flips (either 'T' to 'F' or 'F' to 'T') exceeds k.

• Maximize 'T's and 'F's Separately: We need to find the longest consecutive sequence of 'T's and the longest consecutive sequence of 'F's independently and return the maximum of the two. This is because the optimal solution might involve maximizing either 'T's or 'F's.

• Runtime & Storage Complexity:

  • Runtime: O(n), where n is the length of the answer key.
  • Storage: O(1) - constant extra space.

Code

    def maxConsecutiveAnswers(answerKey: str, k: int) -> int:
    """
    Finds the maximum number of consecutive 'T's or 'F's in the answer key after performing at most k operations.
    """

    def max_consecutive(char: str) -> int:
        """
        Helper function to find the maximum consecutive occurrences of a given character.
        """
        max_length = 0
        left = 0
        flips = 0

        for right in range(len(answerKey)):
            if answerKey[right] != char:
                flips += 1

            while flips > k:
                if answerKey[left] != char:
                    flips -= 1
                left += 1

            max_length = max(max_length, right - left + 1)

        return max_length

    return max(max_consecutive('T'), max_consecutive('F'))