Is Regex Matching

Problem Overview

• Determine for each string whether it matches a simplified regex, returning YES or NO.
• Input: a regex over lowercase letters with '.', '*', and parentheses, and an array arr of k lowercase strings. Output: array of YES/NO.
• Rules: '.' matches one letter; 'X*' matches zero or more; '(...)' is a group with no nested brackets, contains no '', and is always followed by ''.
• Real-world context: NLP regex library at Amazon; asked in Amazon interviews as a coding interview problem and interview question.