Bundle Pricing
This exercise is a common problem in e-commerce and brick-and-mortar retail systems. A customer shops from some form of catalog, selecting items and quantities they wish to purchase. When they are ready, they “check out”, that is, complete their purchase, at which point they are given a total amount of money they owe for the purchase of a specific set of items.
In the bounds of this problem, certain groups of items can be taken together as a “bundle” with a different price. e.g. if I buy a single apple in isolation it costs $1.99, if I buy two apples it’s $2.15. More complex combinations are possible - e.g. a loaf of bread “A” purchased with two sticks of margarine “B” and the second stick of margarine is free (e.g. $0). The same item may appear in more than one bundle, e.g. any one “cart” of items might be able to be combined in more than one way.
For this exercise, produce an API and implementation for a service that accepts a collection of items the customer wishes to purchase (e.g. items and quantities), and produces the lowest possible price for that collection of items. The API is to be called by other applications in the same JVM, e.g. don’t worry about providing a REST or other remote interface to the API, just the actual method calls is fine.
The API is initialized with information that provides all the possible bundles and the catalog of items and their prices. Once it is initialized, many calls can be made at once to the API to produce a total price for collections of items, and it should be able to handle multiple simultaneous calls without errors (e.g. if I’m computing the price for one call, that should not interfere with computing the price for another call).