What is the optimal time complexity of solving Longest Repeating Character Replacement?

The optimized solution achieves a time complexity of O(n) by using sorting, mathematical shortcuts, or hash table lookups.

What is the auxiliary space complexity for Longest Repeating Character Replacement?

The space complexity is O(n) since we only use a minimal/constant amount of extra memory for tracking variables (or auxiliary space if dynamic structures are allocated).

What are the typical edge cases we must handle in Longest Repeating Character Replacement?

Key edge cases include empty collections, negative or large bounds causing integer overflow, arrays with only one element, or inputs where target criteria are not met.

How can we optimize the brute force approach for Longest Repeating Character Replacement?

Brute force methods often inspect all possible combinations. We optimize this by sorting the input list to enable binary search, or tracking processed items in a set to avoid redundant nested loop lookups.

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Longest Repeating Character Replacement

Learn how to solve the 'Longest Repeating Character Replacement' problem. This detailed resource details brute force and optimized approaches.

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Problem Statement

Easy

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 letter. 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.

Write a function characterReplacement(s: str, k: int) -> int.

Constraints

•1 <= len(s) <= 10^5
•s consists of only uppercase English letters
•0 <= k <= len(s)

Examples

Example 1

Input

s = "ABAB", k = 2

Output

Explanation

Replace the two 'A's with 'B's or vice versa to get "BBBB" or "AAAA". The longest substring is 4.

Example 2

Input

s = "AABABBA", k = 1

Output

Explanation

Replace the 'B' at index 3 with 'A' to get "AAAAABA". The longest substring of same characters starting from index 0 is "AAAA" with length 4.

Need a Hint?

Maintain a sliding window boundary using two pointers. Expand the right boundary, and contract the left boundary if criteria are violated.

Edge Cases to Watch

Empty list or null input variables
Single item lists/arrays
Extremely large input bounds causing integer or stack overflow

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