Longest Repeating Character Replacement

You are given a string s and an integer k. You can 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' and form "AABBBBA". The substring "BBBB" has the longest repeating letters, which is 4.

Possible solution: Simple and Naive

Generate all substrings
abc -- a ab abc b bc cUse HashMap to count the number of characters in each substring

banana ------ b -> 1 a -> 3 n -> 2 The maximum number of characters is 'a' => 3 len(banana) = 6 6 - 3 = 3 The number of changes is 6 - 3 = 3 , k = 3 Generate all substrings of banana The total number of substrings are (6, 1) + (6, 2) + (6, 3) + (6, 4) + (6, 5) + (6, 6) = 2^6 - 1 (no empty string) Iterate through all substrings and find the maximum of character count ana a -> 2 n -> 1 m = len(ana) - 2 = 1 if (m == k) then get the length of ana which is 3Source Code

$b/java/LongestRepeatingCharRep.java