Feature #9: Recreating the Decision Tree

Description

Facebook uses a recommendation system to recommend ads to its users. This recommendation system recommends ads on the basis of the results obtained from this decision tree. Facebook wants to implement this recommendation system for Instagram users as well. For this purpose, Facebook wants to replicate the decision tree from a Facebook server to an Instagram server.

The decision tree used in Facebook’s recommendation server is serialized in the form of its inorder and preorder traversals as strings. Using these traversals, we need to create a decision tree for Instagram’s recommendation system.

Let us say we have these preorder and inorder traversals respectively: ["subject", "viewed", "likeable", "notlikeable", "notviewed", "similar", "nonsimilar"] and ["likeable", "viewed", "notlikeable, "subject", "similar", "notviewed", "nonsimilar" ]. The decision tree for these traversals is shown in the illustration below: