Merge K Sorted binary trees
Last updated: June 2, 2026
Quick Overview
Given k sorted binary trees, merge them into a single binary tree that maintains the sorted order of the values. The output should be a balanced binary tree containing all the unique values from the input trees. Each tree is represented by its root node, and the function should return the root of the merged binary tree.
Cloudflare
June 2, 202613
11
3,497 solved
Given k sorted binary trees, merge them into a single binary tree that maintains the sorted order of the values. The output should be a balanced binary tree containing all the unique values from the input trees. Each tree is represented by its root node, and the function should return the root of the merged binary tree.
This coding problem is frequently asked during Technical Screen at Cloudflare. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Cloudflare expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Identify the correct data structure and algorithm for the problem
- Write clean, bug-free code with proper variable naming
- Analyze time and space complexity correctly
- Handle basic edge cases (empty input, single element)
- Communicate your thought process while coding
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 your solution change if the input was sorted?
- How would you test this solution thoroughly?
- What is the worst-case input for your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to merge k sorted binary trees into a single balanced binary tree. We can leverage the 'two pointers' technique effectively here. Each binary tree can be traversed to extract i...
Approach
- Extract Values: Start by performing an in-order traversal on each of the k binary trees to extract their values into a list. For example, if we have three trees with values [1, 3], [2, 4], and ...
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