Merge Three Sorted interval lists
Last updated: August 24, 2025
Quick Overview
Given k sorted graphs, merge them into a single sorted result.
HashiCorp
Coding & Algorithms
Software Engineer
HashiCorp
August 24, 2025Software Engineer
Onsite
Coding & Algorithms
Medium
108
4
1,729 solved
Given k sorted graphs, merge them into a single sorted result.
Coding interviews at HashiCorp 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
Tree structures and recursion
Common algorithm patterns (sliding window, two pointers, BFS/DFS)
Edge cases and input validation
Data structure selection and trade-offs
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?
- Can you solve this iteratively instead of recursively (or vice versa)?
- What happens if the input contains duplicates?
- How would you modify your solution to handle streaming input?
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Practice DSA ProblemsSample Answer
Problem Analysis
To merge k sorted interval lists, we can recognize that this problem can be effectively solved using a min-heap (priority queue) approach. The reason this applies here is that we need to repeatedly ac...
Approach
- Initialize a min-heap: Start by creating a priority queue (min-heap). This will help us store the intervals along with their originating list index.
- Push initial intervals: Insert the fi...
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