← Capital One Interview Insights
Start by clarifying the definition of balanced parentheses (e.g., matching types and proper nesting). Then, propose an efficient stack-based algorithm, walking through the logic and handling edge cases. Finally, discuss time and space complexity and potential optimizations.
Pro tip: Mention that you would validate the input and consider using a dictionary for matching pairs to make the code extensible. Also, note that this problem is a common warm-up for more complex parsing tasks in ML pipelines.
Confirm what characters count as parentheses (e.g., (), [], {}) and whether other characters should be ignored. Ask if the string can be empty or contain only parentheses.
Select a stack (LIFO) to track opening brackets. Explain why a stack is ideal for nested structures.
Iterate through each character: push opening brackets onto the stack; for closing brackets, check if the stack is non-empty and the top matches. If not, return False. After iteration, ensure the stack is empty.
Discuss cases like empty string, single type of parentheses, mismatched types, and extra closing brackets. Mention early termination for efficiency.
State that the algorithm runs in O(n) time and O(n) space in the worst case, where n is the string length.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.