Detect permutation in linked list
Last updated: August 14, 2025
Quick Overview
Given a linked list and a sequence of integers, determine if the linked list contains any permutation of the given sequence as a contiguous sublist. The function should return true if such a permutation exists and false otherwise.
Datadog
August 14, 20255
6
1,781 solved
Given a linked list and a sequence of integers, determine if the linked list contains any permutation of the given sequence as a contiguous sublist. The function should return true if such a permutation exists and false otherwise.
Coding interviews at Datadog 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
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 solve this in a single pass?
- What is the worst-case input for your solution?
- Can you optimize the space complexity of your solution?
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Problem Analysis
The problem requires us to check if a linked list contains any permutation of a given sequence of integers as a contiguous sublist. This hints at a pattern typical in substring search problems, where ...
Approach
- Count Frequencies: First, create a frequency dictionary for the given sequence of integers. For example, if the sequence is [1, 2, 3], the frequency dictionary will be {1: 1, 2: 1, 3: 1}.
- **...
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