Introduction

In this blog post, we will explore how to solve the LeetCode problem "3456" 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 s and an integer k. Determine if there exists a substring of length exactly k in s that satisfies the following conditions: The substring consists of only one distinct character (e.g., "aaa" or "bbb"). If there is a character immediately before the substring, it must be different from the character in the substring. If there is a character immediately after the substring, it must also be different from the character in the substring. Return true if such a substring exists. Otherwise, return false. Example 1: Input: s = "aaabaaa", k = 3 Output: true Explanation: The substring s[4..6] == "aaa" satisfies the conditions. It has a length of 3. All characters are the same. The character before "aaa" is 'b', which is different from 'a'. There is no character after "aaa". Example 2: Input: s = "abc", k = 2 Output: false Explanation: There is no substring of length 2 that consists of one distinct character and satisfies the conditions. Constraints: 1 <= k <= s.length <= 100 s consists of lowercase English letters only.

Explanation

Here's the breakdown of the approach and the Python code:

• High-Level Approach:

  • Iterate through the string s using a sliding window of size k.
  • For each window (substring), check if all characters within the window are the same.
  • If the characters are the same, check if the characters immediately before and after the window (if they exist) are different from the repeating character within the window.

• Complexity:

  • Runtime Complexity: O(n), where n is the length of the string s.
  • Storage Complexity: O(1)

Code

    def solve():
    s = input()
    k = int(input())

    n = len(s)

    for i in range(n - k + 1):
        substring = s[i:i+k]

        # Check if all characters in the substring are the same
        if len(set(substring)) == 1:

            valid = True

            # Check character before the substring
            if i > 0:
                if s[i-1] == substring[0]:
                    valid = False

            # Check character after the substring
            if i + k < n:
                if s[i+k] == substring[0]:
                    valid = False

            if valid:
                return True

    return False

print(solve())