Count maximum path in binary tree
Last updated: January 19, 2026
Quick Overview
Given a binary tree, write a function to count the maximum number of nodes that can be visited along any path from the root to a leaf node. The function should take the root node of the binary tree as input and return an integer representing the maximum path length. A path is defined as a sequence of nodes starting from the root and ending at any leaf node.
SpaceX
January 19, 202621
13
1,420 solved
Given a binary tree, write a function to count the maximum number of nodes that can be visited along any path from the root to a leaf node. The function should take the root node of the binary tree as input and return an integer representing the maximum path length. A path is defined as a sequence of nodes starting from the root and ending at any leaf node.
Coding interviews at SpaceX 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
- 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
- How would you parallelize this solution?
- Can you solve this in a single pass?
- How would you test this solution thoroughly?
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Practice DSA ProblemsSample Answer
Problem Analysis
To solve the problem of counting the maximum path in a binary tree from the root to any leaf node, we will apply a Depth-First Search (DFS) approach. This pattern is appropriate here because we ne...
Approach
- Define the Recursive Function: Create a recursive function that takes a node as an argument and returns the maximum path length from that node to any leaf.
- Base Case: If the node is `Non...
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