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Longest Valid Parentheses

Explore how to identify the longest valid substring of parentheses in a string by applying stack techniques. This lesson helps you understand nested parentheses rules and develop solutions to efficiently solve this classic coding interview problem.

Statement

You are given a string composed entirely of ‘(’ and ‘)’ characters. Your goal is to identify the longest contiguous segment (substring) within this string that represents a “well-formed” or “valid” sequence of parentheses.

A substring is considered valid if:

  1. Every opening parenthesis ‘(’ has a corresponding closing parenthesis ‘)’.

  2. The pairs of parentheses are correctly nested.

Return the length of this longest valid ...