Use a stack to track opening brackets. Iterate through the string, pushing opening brackets and popping when a closing bracket matches the top of the stack. At the end, the stack should be empty for a valid sequence.
Pro tip: Clarify assumptions upfront (e.g., only bracket characters, empty string is valid) and discuss time/space complexity (O(n) time, O(n) space). Mention edge cases like nested and interleaved brackets.
Restate the problem in your own words and confirm requirements with the interviewer. Ask about input constraints and edge cases.
Explain that a stack is ideal because brackets must be closed in LIFO order. Mention that a hash map can map closing brackets to opening brackets for quick lookup.
Describe iterating through each character: if it's an opening bracket, push onto stack; if closing, check if stack is non-empty and top matches, then pop. If not, return false.
Consider empty string (valid), single bracket (invalid), and strings with non-bracket characters (if allowed). Also handle cases where stack is empty when a closing bracket appears.
State time complexity O(n) and space complexity O(n) in worst case. Walk through a few examples to verify correctness.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.