Implement Trie with O(n) time
Last updated: January 12, 2026
Quick Overview
Implement a Trie data structure that supports insert, search, and delete operations, all in O(n) time complexity, where n is the length of the input string. Your implementation should allow for efficient prefix-based queries and should handle edge cases such as inserting and searching for empty strings. Provide a method to return all words stored in the Trie that start with a given prefix.
HubSpot
January 12, 202633
14
1,786 solved
Implement a Trie data structure that supports insert, search, and delete operations, all in O(n) time complexity, where n is the length of the input string. Your implementation should allow for efficient prefix-based queries and should handle edge cases such as inserting and searching for empty strings. Provide a method to return all words stored in the Trie that start with a given prefix.
Coding interviews at HubSpot 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
- 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
- How would you test this solution thoroughly?
- How would you parallelize this solution?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires implementing a Trie (prefix tree) data structure that supports operations: insert, search, and delete, all in O(n) time complexity, where n is the length of the input string. The ...
Approach
- Node Structure: Create a
TrieNodeclass that contains a dictionary to store children nodes and a boolean to indicate whether the node marks the end of a word. - Insert Operation: For e...
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