Detect subsequence in linked list
Last updated: October 23, 2025
Quick Overview
Given a linked list and a sequence of integers, determine if the sequence is a subsequence of the values in the linked list. The function should return true if the sequence can be found in the linked list in the same order, but not necessarily consecutively; otherwise, return false.
Optiver
October 23, 2025109
14
4,076 solved
Given a linked list and a sequence of integers, determine if the sequence is a subsequence of the values in the linked list. The function should return true if the sequence can be found in the linked list in the same order, but not necessarily consecutively; otherwise, return false.
This coding problem is frequently asked during Phone Screen at Optiver. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Optiver expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
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
- Can you optimize the space complexity of your solution?
- What happens if the input contains duplicates?
- How would you modify your solution to handle streaming input?
- How would your solution change if the input was sorted?
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Problem Analysis
The problem requires us to determine if a given sequence of integers is a subsequence of a linked list. The two-pointer technique is a suitable pattern for this problem because we can traverse both th...
Approach
- Initialize two pointers: one for the linked list (
current_node) and one for the sequence (seq_index). - Traverse the linked list using
current_node. For each node in the linked list, check...
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