Count minimum cost in binary tree
Last updated: August 27, 2025
Quick Overview
Given a binary tree, calculate the minimum cost to traverse from the root to any leaf node, where the cost of traversing an edge is defined by the value of the node being traversed. The input will be the root node of the binary tree, and the output should be the minimum cost as an integer.
xAI
August 27, 2025107
10
2,297 solved
Given a binary tree, calculate the minimum cost to traverse from the root to any leaf node, where the cost of traversing an edge is defined by the value of the node being traversed. The input will be the root node of the binary tree, and the output should be the minimum cost as an integer.
xAI uses this problem in the Technical Screen to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
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 test this solution thoroughly?
- Can you solve this iteratively instead of recursively (or vice versa)?
- How would you modify your solution to handle streaming input?
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Problem Analysis
This problem is best approached using Depth-First Search (DFS) due to the recursive nature of tree traversal. The goal is to find the minimum cost path from the root node to any leaf node, where each ...
Approach
- Start at the root node and initialize a variable to keep track of the minimum cost.
- Use a recursive DFS function that takes the current node and the accumulated cost as parameters.
- If the...
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