I knew to use a stack the second I read it, but I fumbled explaining why for a bit.
Clarify the bracket types and edge cases, then propose a stack-based solution that pushes opening brackets and pops for closing brackets, ensuring matches. Walk through an example and analyze time and space complexity.
Pro tip: Mention that you'd handle edge cases like empty string and odd length early, and discuss how to extend the solution to support additional bracket types or streaming input.
Ask which bracket types are included (e.g., (), [], {}) and confirm that an empty string is considered valid. Also clarify if the input can be null or contain non-bracket characters.
Select a stack to track opening brackets, as it naturally handles the LIFO order required for matching brackets.
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 non-empty and the top matches the corresponding opening bracket, then pop. After iteration, the stack must be empty.
Check for empty string (return true), odd length (return false), and null input (return false or throw exception based on requirements). Also handle mismatched brackets and extra closing brackets.
State that the time complexity is O(n) since each character is processed once, and space complexity is O(n) in the worst case (e.g., all opening brackets).
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.