Node Sorter Technical Assessment

Instructions to run the code

Run the command "node ." to run the code.
The output will be in the "output/real-tree.json".

Overview

This is a technical assessment for potential JavaScript Software Engineers.

The purpose of this exercise is to assess your:

Algorithmic skills
Optimisation skills
Code quality
Thinking process

We are not looking for a brute force implementation, but a solution that demonstrates your understanding of the problem statement and data model in tandem with the points above

Programming Languages

Please implement your solution in your preferred language from the below:

JavaScript

Problem Statement

In this exercise you are presented with a flat array of unsorted nodes. Each node has the following properties

nodeId The ID of the node
name A sample property associated with the node
parentId The ID of the parent node
previousSiblingId The ID of the node that appears as direct previous sibling

The input file of nodes can be found here.

The nodes require rearranging, so you are expected to implement a solution that can rearrange this flat array of nodes into a sorted tree structure, where every node is placed under its parent and along with its siblings.

If a null value is given for either parentId or previousSiblingId, that is because it either has no parent (root-level of the tree) or is the first child of its parent, respectively.

If a node is a parent of other node(s), these "children" should appear in an array property called children on the parent node. If a node has no child nodes, this children array will be empty.

You can find the expected output here for clarity.

Examples

Example 1

{
  "nodeId": "8",
  "name": "eight",
  "parentId": "7",
  "previousSiblingId": null
}

The above node has a nodeId of "8". The parentId property of "7" instructs that this node should be in the children array of the node with ID "7". The previousSiblingId property of null instructs that this node does not have a preceding sibling node, so will appear as the first child of node "7".

Example 2

{
  "nodeId": "4",
  "name": "four",
  "parentId": "6",
  "previousSiblingId": "2"
}

The above node has a nodeId of "4". The parentId property of "6" instructs that this node should be in the children array of the node with ID "6". The previousSiblingId property of "2" instructs that this node should be preceded by the node with ID "2" in the children array.

Important Information

You are not expected to mutate any input whilst deriving the output.
There can be many root-level nodes.
Expect that a node can have an arbitrary quantity of siblings.
Expect an arbitrary depth of nodes (children of children).

Deliverables

Your solution (that takes in the provided input and creates the expected output).
Instructions to run the code.
Comments throughout the code that highlights your thinking process.

Your solution will be tested against varying valid inputs.

JSON schemas for both the input and output have been provided if required.

vlbras / node-sorter