Solution: Longest Valid Parentheses
Understand how to apply the stack pattern to identify the longest well-formed parentheses substring in a given string. Learn to use indices in a stack to track unmatched parentheses, calculate valid substring lengths, and achieve an optimal O(n) time solution.
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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:
Every opening parenthesis ‘
(’ has a corresponding closing parenthesis ‘)’.The pairs of parentheses are correctly nested.
Return the length of this longest valid substring.
Constraints:
s.length...