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Problem Statement:

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment. Design an algorithm to serialize and deserialize an N-ary tree. An N-ary tree is a rooted tree in which each node has no more than N children. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that an N-ary tree can be serialized to a string and this string can be deserialized to the original tree structure. For example, you may serialize the following 3-ary tree

as [1 [3[5 6] 2 4]]. Note that this is just an example, you do not necessarily need to follow this format. Or you can follow LeetCode's level order traversal serialization format, where each group of children is separated by the null value.

For example, the above tree may be serialized as [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]. You do not necessarily need to follow the above suggested formats, there are many more different formats that work so please be creative and come up with different approaches yourself.


Please understand the problem really well and spend some time think through some possible solutions for the problem before perusing the rest of the chapter. Feel free to take help from Binary Tree (De)Serialization

We could definitely use Breadth First Search (BFS) to encode (serialize) an N-ary tree. But the main challenge lies in: while decoding how to know how many child nodes a specific node has. You could become really creative and come up with multiple ways to achieve it. What we are looking for here is a delimiter. For our solution I would use Dollar sign '$' to denote when the sequence of child nodes for a specific node ends. If a node has no child node then we would only put '$'.
The below code implements what I just described.

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For below n-ary tree:

we would get below serialization string:

Related Problems:

The above content is written by:

Abhishek Dey

Abhishek Dey

A Visionary Software Engineer With A Mission To Empower Every Person & Every Organization On The Planet To Achieve More

Microsoft | University of Florida

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