Get Special Substring (MTS)

Problem Overview

• Given a string s and a 26-bit charValue mapping letters as special (1) or normal (0), find the length of the longest substring containing at most k normal characters.
• Inputs: s, integer k, and charValue; Output: an integer length of the longest valid substring.
• Context: models text processing in a language where only some letters are special, affecting allowable substrings.
• A coding interview problem and interview question focused on string constraints and validation.