Validate string balanced
Last updated: January 31, 2026
Quick Overview
Given a string consisting of parentheses, brackets, and braces, write a function to determine if the string is balanced. A string is considered balanced if every opening symbol has a corresponding closing symbol in the correct order. The function should return a boolean value: true if the string is balanced and false otherwise.
Waymo
January 31, 202681
9
830 solved
Given a string consisting of parentheses, brackets, and braces, write a function to determine if the string is balanced. A string is considered balanced if every opening symbol has a corresponding closing symbol in the correct order. The function should return a boolean value: true if the string is balanced and false otherwise.
This coding problem is frequently asked during Take-home Project at Waymo. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Waymo expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Recognize the underlying problem pattern (sliding window, two pointers, BFS/DFS, etc.)
- Discuss multiple approaches and trade-offs before coding
- Implement an optimal solution with clean, production-quality code
- Handle all edge cases including boundary conditions and invalid input
- Optimize both time and space complexity with clear justification
- Test your solution systematically with well-chosen examples
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- Can you solve this in a single pass?
- What happens if the input contains duplicates?
- How would you parallelize this solution?
- How would you test this solution thoroughly?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to determine if a string containing parentheses '()', brackets '[]', and braces '{}' is balanced. A balanced string means that every opening symbol must have a corresponding cl...
Approach
- Initialize an empty stack to keep track of opening symbols.
- Create a mapping of closing symbols to their corresponding opening symbols for easy lookup.
- Traverse the string character by charac...
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