Valid Parentheses Solution with Stack and HashMap

LeetCode #20 – Valid Parentheses | Python Implementation I implemented a stack-based validation approach to verify balanced parentheses. A HashMap maps each closing bracket to its corresponding opening bracket. As we iterate through the string, opening brackets are pushed onto the stack. When a closing bracket is encountered, we check if the stack's top matches its required opening bracket using the HashMap — if it does, we pop; otherwise, the sequence is invalid. After processing all characters, a valid string must leave the stack empty. This pattern is fundamental in compiler design, syntax validators, and expression parsers used across programming language interpreters. Key Takeaway: Using a HashMap to map closing brackets to their required opening counterparts simplifies the matching logic and avoids nested conditionals. The stack naturally handles nested structures, and checking for an empty stack at the end ensures all opened brackets were properly closed. Time: O(n) | Space: O(n) #LeetCode #DataStructures #Python #Stack #HashMap #CodingInterview #ProblemSolving #SoftwareEngineering

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