Stack-based solution, not complicated in theory.
Use a stack to track opening brackets. Iterate through the string, pushing opening brackets and popping when a closing bracket is encountered, ensuring it matches the top of the stack. At the end, the stack should be empty.
Pro tip: Clarify assumptions about the input, such as whether the string contains only brackets or other characters, and discuss handling of edge cases like empty strings or unbalanced brackets. Mention time and space complexity upfront.
Restate the problem to ensure clarity: check if every opening bracket has a corresponding closing bracket of the same type and they are properly nested. Ask clarifying questions about input constraints.
Explain that a stack is ideal because brackets must be closed in last-in-first-out 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 it's a closing bracket, check if stack is non-empty and top matches, then pop. If mismatch or empty stack, return false.
Discuss cases like empty string (return true), string with no brackets (return true), string with only opening brackets (return false), and strings with other characters (ignore them).
State time complexity O(n) and space complexity O(n) in worst case. Walk through a few examples to verify correctness, including nested and interleaved brackets.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.