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Solution: Longest Valid Parentheses

Explore how to use the stack pattern to identify the longest valid parentheses substring in a given string. Understand the algorithm that tracks indices to handle nested pairs and calculate lengths effectively, optimizing your problem-solving approach with stacks.

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 substring.

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