Longest Repeating Character Replacement

Problem: Longest Repeating Character Replacement

Given a string s and an integer k, you are allowed to choose any character of the string and change it to any other uppercase English character. You can perform this operation at most k times.

Return the length of the longest substring containing the same letter you can get after performing the above operations.

Example 1:

Input: s = "ABAB", k = 2  
Output: 4  
Explanation: Replace the two 'A's with two 'B's or vice versa.

Example 2:

Input: s = "AABABBA", k = 1  
Output: 4  
Explanation: Replace the one 'A' in the middle with 'B' to form "AABBBBA".

Constraints:

• 1 <= s.length <= 10⁵
• s consists of only uppercase English letters.
• 0 <= k <= s.length