Count median in binary tree
Last updated: April 4, 2026
Quick Overview
Given a binary tree, write a function to calculate the median value of all the nodes in the tree. The median is defined as the middle value when the values are sorted in ascending order; if there is an even number of values, return the average of the two middle values. Your function should take the root node of the binary tree as input and return the median as a float.
Twitter/X
April 4, 20261
11
2,766 solved
Given a binary tree, write a function to calculate the median value of all the nodes in the tree. The median is defined as the middle value when the values are sorted in ascending order; if there is an even number of values, return the average of the two middle values. Your function should take the root node of the binary tree as input and return the median as a float.
This coding problem is frequently asked during Onsite at Twitter/X. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Twitter/X 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?
- Can you optimize the space complexity of your solution?
- Can you solve this in a single pass?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires calculating the median of the values in a binary tree. The median is defined as the middle value when the values are sorted. Since we need to traverse the entire tree to gather al...
Approach
- Traverse the Tree: Use a DFS to visit each node and collect the values into a list. For example, if the tree has nodes with values [5, 3, 8, 1, 4], we will gather these during traversal.
- **S...
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