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Bytedance·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Bytedance software engineering interview with a classic bracket validation problem. Pretty standard algorithmic screen, nothing too wild, but the kind of question where you either know the pattern cold or you start second-guessing yourself mid-solution.

Questions Asked (1)

Q1

Given a string containing only bracket characters, write a function to determine whether the brackets are all properly matched and closed in the correct order.

Algorithms & Data Structures
Author's notes

Stack problem, pretty textbook.

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AI HintsAI Generated

Suggested Approach

Use a stack to track opening brackets and validate closing brackets in order. Iterate through the string, pushing opening brackets and popping when a matching closing bracket is encountered. At the end, the stack should be empty for a valid string.

Pro tip: Clarify the bracket types (e.g., (), [], {}) and whether the string can contain non-bracket characters. Also, discuss edge cases like empty string and single bracket, and mention time/space complexity upfront.

1. Clarify requirements and edge cases

Ask if only bracket characters are allowed and which types. Confirm edge cases: empty string, single bracket, nested and interleaved brackets.

2. Choose the right data structure

Select a stack (LIFO) because brackets must be closed in reverse order of opening. Explain why a queue or other structure wouldn't work.

3. Outline the algorithm

Iterate through each character: if opening bracket, push onto stack; if closing bracket, check if stack is empty or top doesn't match, return false; otherwise pop. After loop, return true only if stack is empty.

4. Analyze complexity and test

State time complexity O(n) and space O(n) in worst case. Walk through examples like '()[]{}', '([)]', and '(((' to validate.

Key Points to Mention

  • Stack data structure and its LIFO property
  • Mapping of closing brackets to opening brackets
  • Handling of mismatched types (e.g., '(]')
  • Early termination when a closing bracket appears with empty stack
  • Final check for empty stack to ensure all brackets closed
  • Time and space complexity analysis

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.