Maximize Repeated Substring Length

Problem Overview

• Given a string of lowercase letters and '?', replace each '?' to maximize the length of the longest repeated substring.
• A repeated substring is even-length where the first half equals the second; output the maximum achievable length as an integer.
• Input: single string S; Output: one integer; substrings are contiguous.
• Domain: string processing/pattern detection; relevant to practical text manipulation.
• Asked in Amazon interviews; a classic coding interview problem and interview question.