Merge K Sorted binary trees
Last updated: February 16, 2026
Quick Overview
Given three sorted graphs, merge them into a single sorted result.
PlanetScale
Coding & Algorithms
Software Engineer
PlanetScale
February 16, 2026Software Engineer
Technical Screen
Coding & Algorithms
Easy
14
12
1,444 solved
Given three sorted graphs, merge them into a single sorted result.
PlanetScale uses this problem in the Technical Screen to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
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
Graph algorithms and traversal
Binary search and divide and conquer
Edge cases and input validation
Tree structures and recursion
Time and space complexity analysis
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
- What is the worst-case input for your solution?
- How would you modify your solution to handle streaming input?
- What if the input doesn't fit in memory?
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Practice DSA ProblemsSample Answer
Problem Analysis
To merge K sorted binary trees, we can utilize a priority queue (min-heap) to efficiently get the smallest element from the K trees at each step. Since the trees are sorted, this approach allows us to...
Approach
- Initialize a min-heap to keep track of the smallest elements from each tree.
- Push the root of each binary tree into the min-heap.
- While the min-heap is not empty:
- Extract the minimum ele...
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