Greedy on linked list
Last updated: April 6, 2026
Quick Overview
Given a singly linked list, implement a function that uses a greedy algorithm to rearrange the nodes in such a way that every alternate node is greater than its adjacent nodes. The function should return the modified linked list. The input will be the head of the linked list, and the output should be the head of the rearranged linked list.
Two Sigma
April 6, 20268
11
699 solved
Given a singly linked list, implement a function that uses a greedy algorithm to rearrange the nodes in such a way that every alternate node is greater than its adjacent nodes. The function should return the modified linked list. The input will be the head of the linked list, and the output should be the head of the rearranged linked list.
Two Sigma 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
- 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
- How would your solution change if the input was sorted?
- Can you solve this in a single pass?
- How would you modify your solution to handle streaming input?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires rearranging a singly linked list so that every alternate node is greater than its adjacent nodes. This suggests a pattern where we might want to use a greedy approach, as we can t...
Approach
- Initialization: Start by checking if the head of the linked list is null or if there's only one node. If so, return the head directly, as no rearrangement is needed.
- Traversal: Use a poi...
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