Get Longest Substring

Problem Overview

• Given a lowercase product name string s, find the length of the longest substring longer than 1 where the first character is lexicographically smaller than the last.
• Input: string s (2 ≤ n ≤ 1e5); Output: int length of the longest valid substring, or 0 if none.
• Context: Amazon product search team analyzing product names.
• From Amazon interviews; a common coding interview problem and interview question.