Find a Corresponding Node of a Binary Tree in a Clone of That Tree

Find a Corresponding Node of a Binary Tree in a Clone of That Tree

What is this problem about?

The Find a Corresponding Node of a Binary Tree in a Clone of That Tree interview question presents a scenario where you have two identical binary trees: an original tree and a cloned version. You are given a reference to a specific node in the original tree, and your goal is to find and return the reference to the exact same node in the cloned tree. Since the trees are structural clones with the same values, the challenge is to traverse both simultaneously or use the original's structure to navigate the clone.

Why is this asked in interviews?

Companies like Meta, Amazon, and Bloomberg use this problem to test a candidate's fundamental understanding of tree structures and traversal methods. It evaluations your ability to handle multiple tree references at once and ensures you understand that while the node values might be the same, the memory addresses are different. The Binary Tree interview pattern here also checks if you can implement a solution that works even if duplicate values exist in the tree, which forces you to rely on structural traversal rather than simple value matching.

Algorithmic pattern used

This problem is primarily solved using either the Depth-First Search (DFS) interview pattern or the Breadth-First Search (BFS) interview pattern. You traverse both trees in parallel. Starting from the roots, whenever you move to a left or right child in the original tree, you move to the corresponding left or right child in the cloned tree. When you reach the target node in the original tree, the current node in the cloned tree is your answer.

Example explanation

Suppose we have a simple tree: Original: Root(7) -> Left(4), Right(3). Clone: Root'(7) -> Left'(4), Right'(3). Target Node: The node with value 3 in the original tree.

1. Start at Root(7) and Root'(7).
2. Root(7) is not the target.
3. Move to the left children: 4 and 4'. Node 4 is not the target.
4. Move back and then to the right children: 3 and 3'.
5. Node 3 matches the target reference.
6. Return the reference to Node 3' from the cloned tree.

Common mistakes candidates make

• Comparing values instead of references: If the tree has duplicate values, simply searching for a node with the same value as the target will fail. You must compare the actual memory reference (original_node == target).
• Forgetting null checks: Not checking if a node is null before accessing its children, which leads to runtime errors.
• Redundant traversal: Searching the entire tree even after the target node has been found in one branch.

Interview preparation tip

When working with cloned structures, remember that the relative path from the root to any node is identical in both the original and the clone. This "parallel traversal" mindset is a key part of the Tree interview pattern and is useful for many object-oriented design problems where deep copies are involved.