Merge K Sorted binary trees
Last updated: March 31, 2026
Quick Overview
Given k sorted grids, merge them into a single sorted result.
Palantir
Coding & Algorithms
Software Engineer
Palantir
March 31, 2026Software Engineer
Phone Screen
Coding & Algorithms
Easy
0
12
4,495 solved
Given k sorted grids, merge them into a single sorted result.
Palantir uses this problem in the Phone 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
Sorting and searching
Hash maps and frequency counting
Graph algorithms and traversal
Binary search and divide and conquer
Dynamic programming and memoization
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
- How would you parallelize this solution?
- What if the input doesn't fit in memory?
- How would your solution change if the input was sorted?
- How would you modify your solution to handle streaming input?
Sharpen Your Skills on Codemia
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Practice DSA ProblemsSample Answer
Problem Analysis
To merge k sorted grids into a single sorted result, we can leverage a min-heap (or priority queue) to efficiently extract the smallest elements across the multiple grids. The reason this approach is ...
Approach
- Initialization: Create a min-heap to store the top element of each grid along with its grid index and the element index.
- Heap Population: Insert the first element of each grid into the h...
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