How should I practice Serialize and Deserialize a Binary Tree?

Start by reading the full statement, solve the visible examples, then compare the pattern against related NVIDIA phone screen problems in FastPrep.

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FastPrep tags this as a NVIDIA phone screen coding practice problem when the problem catalog has that company and stage context.

Serialize and Deserialize a Binary Tree

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Problem statement

Implement both directions of a binary-tree codec. Encode root and independently decode the supplied data; they need not describe the same tree.

For this exercise, assume preorder serialization: a node emits its signed decimal value, then its left subtree, then its right subtree. A null pointer emits #. Separate tokens with one comma and use no spaces or trailing comma.

Return two strings in order: the exact preorder encoding of root, and the decoded data tree represented as compact level-order JSON. Keep interior null positions and remove trailing nulls; represent an empty decoded tree as []. The supplied data is a valid canonical preorder encoding.

Function

binaryTreeCodec(root: TreeNode, data: String) → String[]

Examples

Example 1

root = [1,2,3,null,null,4,5]data = "8,#,9,#,#"return = ["1,2,#,#,3,4,#,#,5,#,#","[8,null,9]"]

Encode the supplied tree, then decode an unrelated right-child tree independently.

Example 2

root = []data = "#"return = ["#","[]"]

A null tree is # in preorder and [] in trimmed level order.

Example 3

root = [-7,null,3,-1]data = "0,-2,#,#,0,#,#"return = ["-7,#,3,-1,#,#,#","[0,-2,0]"]

Negative values, missing children and duplicate decoded values preserve their positions.

Constraints

For this exercise, assume each input tree has from 0 through 500 nodes, and values satisfy -10^6 <= value <= 10^6.
Decimal tokens have no leading zeros or plus sign; zero is 0.
The trees are finite, acyclic binary trees. Decoding must preserve every value and left/right link.