Validate linked list sorted
Last updated: February 28, 2026
Quick Overview
Given a singly linked list, write a function to determine if the list is sorted in non-decreasing order. The function should return a boolean value: true if the list is sorted, and false otherwise. The input will be the head node of the linked list, and the output should be a single boolean.
Jump Trading
February 28, 20268
11
1,799 solved
Given a singly linked list, write a function to determine if the list is sorted in non-decreasing order. The function should return a boolean value: true if the list is sorted, and false otherwise. The input will be the head node of the linked list, and the output should be a single boolean.
This coding problem is frequently asked during Technical Screen at Jump Trading. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Jump Trading 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
- How would your solution change if the input was sorted?
- How would you parallelize this solution?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Problem Analysis
The problem requires us to validate whether a singly linked list is sorted in non-decreasing order. The most appropriate pattern for this task is linear traversal, as we need to compare each node's va...
Approach
- Start at the head of the linked list.
- Initialize a current node pointer to the head.
- Loop through the linked list until the current node is not None:
- Compare the current node's value wit...
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