Find kth largest element in binary tree
Last updated: January 28, 2026
Quick Overview
Given a binary tree, write a function to find the k-th largest element in the tree. You should traverse the tree efficiently and return the k-th largest value as an integer. The input will consist of the root node of the binary tree and an integer k, and you can assume that k is always valid.
Grafana Labs
January 28, 2026210
10
2,843 solved
Given a binary tree, write a function to find the k-th largest element in the tree. You should traverse the tree efficiently and return the k-th largest value as an integer. The input will consist of the root node of the binary tree and an integer k, and you can assume that k is always valid.
This coding problem is frequently asked during Phone Screen at Grafana Labs. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Grafana Labs expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
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?
- What is the worst-case input for your solution?
- How would your solution change if the input was sorted?
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Problem Analysis
To find the k-th largest element in a binary tree, we can utilize the properties of a binary search tree (BST) if the tree is structured as such. However, since the problem does not explicitly state t...
Approach
- Start with a recursive function that performs a reverse in-order traversal of the tree.
- Maintain a counter to track how many nodes have been visited. When the counter reaches k, we have found ou...
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