Binary Search on linked list
Last updated: January 10, 2026
Quick Overview
Implement a binary search algorithm on a singly linked list to determine if a given target value exists within the list. The linked list will be sorted in ascending order, and your function should return true if the target is found and false otherwise. You may assume that the linked list has a known length.
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January 10, 202624
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Implement a binary search algorithm on a singly linked list to determine if a given target value exists within the list. The linked list will be sorted in ascending order, and your function should return true if the target is found and false otherwise. You may assume that the linked list has a known length.
This coding problem is frequently asked during Phone Screen at Postmates. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Postmates expects candidates to write production-quality code, not just solve the puzzle.
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
- What happens if the input contains duplicates?
- How would your solution change if the input was sorted?
- How would you test this solution thoroughly?
- How would you modify your solution to handle streaming input?
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Practice DSA ProblemsSample Answer
Problem Analysis
In this problem, we need to perform a binary search on a singly linked list. Binary search typically requires random access to elements, which is not feasible with linked lists since they are sequenti...
Approach
- Get the Length: First, traverse the linked list to determine its length. This will help us establish the boundaries for our binary search.
- Binary Search Process: We will maintain two po...
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