Binary Trees and Binary Search Trees Questions

Focuses on tree data structures, specifically binary trees and binary search trees. Candidates should understand node relationships, common traversals including in order, pre order, post order, and level order, and be able to implement traversals both recursively and iteratively. Cover binary search tree properties and operations including search, insertion, deletion, validation of binary search tree property, and finding the lowest common ancestor. Include problems on tree paths, height and balance calculations, serialization and deserialization, checking and restoring balance at a high level, and use cases in system design. Emphasize complexity analysis, recursion versus iterative solutions using stacks or queues, and handling edge cases such as duplicate keys and degenerate trees.

EasyTechnical

0 practiced

Implement level-order traversal (breadth-first) for a binary tree in Python. Assume TreeNode as above. The function should return a list of lists where each inner list contains values at one level. Aim for O(n) time and O(width) extra space. Example: tree with level arrays [1], [2,3], [4,5,6] should return [[1],[2,3],[4,5,6]].

MediumTechnical

0 practiced

Implement BST search and insertion methods in Python. Choose and explicitly state a duplicate key policy (for example, store an integer count at the node when inserting a duplicate). Provide recursive and iterative implementations for insert, ensure correctness, and analyze time/space complexity. Show a short example demonstrating your chosen duplicate policy.

MediumTechnical

0 practiced

Design serialize(root) and deserialize(data) functions for a binary tree in Python. Choose and describe your format (e.g., preorder with null markers or level-order with placeholders), implement both functions, and show an example mapping between a small tree and the serialized string such as '1,2,#,#,3,4,#,#,5,#,#'. Discuss trade-offs between readability and compactness.

MediumTechnical

0 practiced

Design and implement two algorithms to validate whether a binary tree is a valid BST: (1) recursive method using allowable min/max ranges passed down the recursion, and (2) iterative method using stack and inorder traversal checking monotonicity. Both should be O(n) time. Explain how your approach handles duplicate keys under different duplicate policies.

HardTechnical

0 practiced

Two very large BSTs are stored on disk such that neither fits entirely into memory. Design an algorithm to compute the intersection of keys (common elements) using O(h1 + h2) memory where h1 and h2 are tree heights, minimizing disk I/O. Provide a streaming-aware approach (e.g., synchronous inorder traversals) and discuss performance trade-offs.

Unlock Full Question Bank

Get access to hundreds of Binary Trees and Binary Search Trees interview questions and detailed answers.

Join thousands of developers preparing for their dream job.