Medium

Quiz

#424 Longest Repeating Character Replacement

APPROACH

Given a string s and an integer k, you may replace at most k characters with any uppercase English letter. Return the length of the longest substring that consists of a single repeated letter after performing at most k replacements.

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.

There may exists other ways to achieve this answer too.

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What is the optimal approach for this problem?