Valid Parentheses in Java: Why a Stack Is the Right Tool for the Job
Valid Parentheses looks like a simple string problem, right up until you try to solve it without a Stack and end up rebuilding one badly by hand. It's one of the most asked interview questions for a reason — it's a two-minute check on whether you actually understand Last In, First Out, or whether you're improvising something that only happens to work on the examples in front of you.
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