Count median in linked list
Last updated: December 31, 2025
Quick Overview
Given a singly linked list of integers, write a function to calculate and return the median value of the elements in the list. If the list has an odd number of elements, return the middle element; if it has an even number of elements, return the average of the two middle elements. The function should handle edge cases, such as an empty list, by returning a suitable value (e.g., null or 0).
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December 31, 202530
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Given a singly linked list of integers, write a function to calculate and return the median value of the elements in the list. If the list has an odd number of elements, return the middle element; if it has an even number of elements, return the average of the two middle elements. The function should handle edge cases, such as an empty list, by returning a suitable value (e.g., null or 0).
Coding interviews at ServiceNow 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
- Identify the correct data structure and algorithm for the problem
- Write clean, bug-free code with proper variable naming
- Analyze time and space complexity correctly
- Handle basic edge cases (empty input, single element)
- Communicate your thought process while coding
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 is the worst-case input for your solution?
- What if the input doesn't fit in memory?
- Can you solve this in a single pass?
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Practice DSA ProblemsSample Answer
Problem Analysis
To find the median of a singly linked list, we need to identify the middle elements of the list. This involves understanding the linked list structure and how to traverse it. The median is defined dif...
Approach
- Initialize two pointers:
slowandfast. Start both at the head of the linked list. - Move
slowone step at a time andfasttwo steps at a time. By the timefastreaches the end of the li...
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