Validate string complete
Last updated: December 28, 2025
Quick Overview
Given a string, implement a function to validate if it is a complete representation of a valid expression, ensuring that all opening brackets have corresponding closing brackets in the correct order. The function should return a boolean value: true if the string is valid, and false otherwise. Consider various types of brackets, including parentheses '()', square brackets '[]', and curly braces '{}'.
Amazon
December 28, 2025300
11
2,623 solved
Given a string, implement a function to validate if it is a complete representation of a valid expression, ensuring that all opening brackets have corresponding closing brackets in the correct order. The function should return a boolean value: true if the string is valid, and false otherwise. Consider various types of brackets, including parentheses '()', square brackets '[]', and curly braces '{}'.
Coding interviews at Amazon focus on problem-solving approach as much as the final solution. The interviewer wants to see you break down the problem, consider edge cases, and optimize iteratively. Communication throughout the process is key.
What the Interviewer Expects
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
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 optimize the space complexity of your solution?
- What happens if the input contains duplicates?
- How would you test this solution thoroughly?
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Practice DSA ProblemsSample Answer
Problem Analysis
To determine if a string is a valid expression with respect to brackets, we can identify this problem as one that can be effectively solved using a stack data structure. The stack allows us to kee...
Approach
- Initialize an empty stack to keep track of opening brackets.
- Create a mapping of closing brackets to their corresponding opening brackets for quick lookup.
- Iterate through each character in t...
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