Transform linked list to tree
Last updated: January 18, 2026
Quick Overview
Given a singly linked list, transform it into a balanced binary search tree (BST). The linked list is sorted in ascending order, and you should return the root node of the resulting BST. Ensure that the tree maintains the properties of a binary search tree while being balanced.
OpenAI
January 18, 20265
6
4,629 solved
Given a singly linked list, transform it into a balanced binary search tree (BST). The linked list is sorted in ascending order, and you should return the root node of the resulting BST. Ensure that the tree maintains the properties of a binary search tree while being balanced.
Coding interviews at OpenAI 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
- Can you optimize the space complexity of your solution?
- Can you solve this iteratively instead of recursively (or vice versa)?
- How would your solution change if the input was sorted?
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Problem Analysis
The problem requires transforming a sorted singly linked list into a balanced binary search tree (BST). The key characteristics of this problem are:
- Sorted Input: The linked list is sorted in ...
Approach
To transform the linked list into a balanced BST, we can follow these steps:
- Convert Linked List to Array: First, traverse the linked list to create an array representation. This allows us to ...
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