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Coding & Algorithms questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master coding & algorithms interviews.

What difficulty level is this interview question?

This is a hard difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at Amazon.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at Amazon during technical interviews.

Serialize and deserialize a binary tree | Amazon Interview Question

Quick Overview

This question evaluates competency in designing robust serialization formats and manipulating binary tree data structures, including preservation of structure and node values, handling nulls, and reasoning about time and space complexity; it sits in the Coding & Algorithms domain (data structures/trees) and requires practical implementation skills alongside conceptual understanding. It is commonly asked to measure a candidate's ability to produce reproducible data representations, handle edge cases such as empty or sparse trees, and reason about performance and correctness for large inputs.

Problem

Design two functions to serialize and deserialize a binary tree.

Serialize : convert a binary tree into a single string.
Deserialize : reconstruct the exact same binary tree from that string.

Assume the tree nodes are:

val is an integer (may be negative)
left / right pointers may be null

Requirements

deserialize(serialize(root)) must produce a tree structurally identical to root with the same node values.
Your format must handle:
- empty tree
- missing children (nulls) in arbitrary positions
- large trees (e.g., up to ~10^5 nodes), so time and space complexity matter
Explain your chosen encoding format and analyze complexity.

Example

If the tree is:

1 as root
left child 2
right child 3 with children 4 and 5

Your serialized output could look like (format is up to you):

"1,2,#,#,3,4,#,#,5,#,#"

where # indicates null.

Quick Overview

Problem

Design two functions to serialize and deserialize a binary tree.

Serialize : convert a binary tree into a single string.

Deserialize : reconstruct the exact same binary tree from that string.

Assume the tree nodes are:

val is an integer (may be negative)

left / right pointers may be null

Requirements

deserialize(serialize(root)) must produce a tree structurally identical to root with the same node values.

Your format must handle:

empty tree
missing children (nulls) in arbitrary positions
large trees (e.g., up to ~10^5 nodes), so time and space complexity matter

Explain your chosen encoding format and analyze complexity.

Example

If the tree is:

1 as root

left child 2

right child 3 with children 4 and 5

Your serialized output could look like (format is up to you):

"1,2,#,#,3,4,#,#,5,#,#"

where # indicates null.

Serialize and deserialize a binary tree

Quick Overview

Problem

Requirements

Example

Submit Your Answer

Serialize and deserialize a binary tree

Quick Overview

Problem

Requirements

Example

Submit Your Answer