Brute force Approach

Algorithm

We are given a string and an integer k, and we can change at most k characters to make the string contain all the same characters in any chosen window. So the brute-force way would be to check every possible substring, and for each one, calculate how many characters we need to replace to make all characters in that substring the same. If that number is ≤ k, we update our answer.

Loop over each possible starting position of the substring.
From each starting point, expand the end position one by one to form all substrings.
Track the frequency of characters in the current substring.
Find the most frequent character in this substring.
Calculate how many characters need to be changed to make all characters the same.
If the number of required changes is within the allowed limit, update the maximum length.
Repeat this for all starting positions.