Use a stack to track opening brackets. Iterate through the string: push opening brackets onto the stack; for closing brackets, check if the stack is non-empty and the top matches the corresponding opening bracket. At the end, the stack must be empty for the string to be valid.
Pro tip: Clarify edge cases upfront (empty string, odd length, non-bracket characters) and mention that early termination on odd length or mismatched closing bracket improves efficiency. Also, discuss time and space complexity: O(n) time and O(n) space in the worst case.
Restate the problem to ensure clarity. Identify edge cases: empty string (valid), odd length (invalid), strings with only opening or only closing brackets, and strings with mixed bracket types.
Select a stack (LIFO) to track opening brackets. Explain why a stack is ideal: the most recent opening bracket must be closed first, matching the LIFO principle.
Iterate through each character. If it's an opening bracket, push it onto the stack. If it's a closing bracket, check if the stack is empty or if the top doesn't match the corresponding opening bracket; if so, return false. Otherwise, pop the stack.
After iteration, return true only if the stack is empty. Analyze time complexity O(n) and space complexity O(n) in the worst case. Mention potential optimizations like early exit on odd length.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.