We have a string s of length n, which consist only UPPERCASE characters and we have a number k (always less than n and greater than 0). We can make at most k changes in our string such that we can get a sub-string of maximum length which have all same characters.
 

Example 1:

Input: s = "ABAB", k = 2
Output: 4
Explanation: Change 2 'B' into 'A'.

Example:

Input: s = "ABCD", k = 1
Output: 2
Explanation: Change one 'B' into 'A'.

Your Task:
You don't need to read print anything. Your task is to complete the function characterReplacement() which takes s and k as input parameter and returns the maximum length of sub-string after doing k changes.
 

Expected Time Complexity: O(n)
Expected Space Complexity: O(26)
 

Constraints:
1 <= n <= 10⁴