Serialize and Deserialize Binary Tree in DSA C++ - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does it mean to serialize a binary tree?

Serialization means converting a binary tree into a string or list format so it can be stored or sent easily.

beginner

What is the purpose of deserialization in binary trees?

Deserialization means converting the stored string or list back into the original binary tree structure.

intermediate

Why do we use a special marker like '#' or 'null' during serialization?

We use markers to represent empty (null) child nodes so the tree structure can be fully recovered during deserialization.

intermediate

Which tree traversal method is commonly used for serialization and why?

Preorder traversal is commonly used because it records the root first, then left and right subtrees, making it easy to reconstruct the tree.

intermediate

What is the time complexity of serializing and deserializing a binary tree?

Both serialization and deserialization take O(n) time, where n is the number of nodes, because each node is visited once.

What does the '#' symbol usually represent in serialized binary trees?

A A duplicate node

B A null or empty child node

C The root node

D A leaf node

The '#' symbol is used to mark null or empty child nodes during serialization.

Which traversal order is best suited for serializing a binary tree to preserve structure?

A Preorder

B Inorder

C Postorder

D Level order

Preorder traversal records root first, then left and right children, which helps in reconstructing the tree.

What is the main goal of deserializing a binary tree?

A Convert string back to original tree structure

B Print the tree nodes

C Count the number of nodes

D Balance the tree

Deserialization rebuilds the original tree from the serialized string.

If a binary tree has 7 nodes, what is the time complexity to serialize it?

A O(n^2)

B O(log 7)

C O(1)

D O(7)

Serialization visits each node once, so time is proportional to number of nodes, O(n).

Why can't we use inorder traversal alone for serialization?

A It is slower than preorder

B It skips leaf nodes

C It does not uniquely identify tree structure

D It requires extra memory

Inorder traversal alone cannot reconstruct the tree uniquely because different trees can have the same inorder sequence.

Explain how you would serialize a binary tree using preorder traversal including null markers.

Think about visiting nodes root-left-right and marking empty spots.

Describe the steps to deserialize a serialized string back into the original binary tree.

Use the order of values and null markers to rebuild the tree step by step.