Seemed easy and it basically was, but I almost over-engineered it by adding case folding before re-reading the prompt.
Start by clarifying that the comparison is exact, with no normalization. Then present a two-pointer approach that compares characters from both ends moving inward, returning false on the first mismatch. Discuss time and space complexity, and mention edge cases like empty strings and single characters.
Pro tip: Mention that you would confirm with the interviewer whether Unicode or multi-byte characters need special handling, since exact comparison can be tricky with different encodings. Also, note that a recursive solution is possible but iterative is more efficient in Python due to recursion limits.
Confirm that the comparison is exact, with no case normalization or punctuation handling, and discuss how to handle empty strings and single characters.
Select a two-pointer technique for O(n) time and O(1) space, or consider reversing the string for a simpler but less efficient solution.
Write clean code with meaningful variable names, handling edge cases and returning a boolean.
Walk through test cases like 'racecar' (true), 'hello' (false), 'Aba' (false due to case), and empty string (true).
State that the two-pointer approach runs in O(n) time and O(1) space, and discuss trade-offs with other methods.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Use a stack to track opening brackets and validate closing brackets against the most recent opening. Iterate through the string, pushing opening brackets and popping for closing brackets, ensuring the popped bracket matches the closing type. At the end, the stack must be empty for a valid sequence.
Pro tip: Always discuss edge cases like empty strings, strings with odd length, and strings with only opening or only closing brackets. Also, mention that this approach runs in O(n) time and O(n) space, which is optimal for this problem.
Confirm that the string contains only bracket characters and that we need to check for correct nesting and matching types. Ask if an empty string is considered valid.
Explain that a stack is ideal because it follows Last-In-First-Out (LIFO) order, which naturally handles nested 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 empty or if the top doesn't match, return false. Otherwise, pop the stack.
After the loop, ensure the stack is empty. Also, consider early termination for odd-length strings or strings with invalid characters.
State that the time complexity is O(n) because we process each character once, and space complexity is O(n) in the worst case for the stack.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.