Backend Developer Interview Task

Goal

Implement an algorithm to detect flight schedule changes in airline competitive landscape.

Description

You are creating an application, to be used by airline agencies, for detecting cases of airlines introducing new or discontinuing existing regular flight schedules. For example, Lufthansa is offering a flight from Berlin to Vienna every Monday at 7:30. In the case that Lufthansa decides to stop offering that flight, we need to be able to detect that, because that opens a business opportunity for flight agencies to offer alternative flights. The same applies to newly introduced flight schedules.

Change detection algorithm

`New flights`

A flight with departure time T is considered to be a new flight if no corresponding flight from same airline exists with departure time T’ = T - 7 days (+/- 30 minutes tolerance).

`Discontinued flights`

A flight with departure time T is considered to be discontinued if no corresponding flight from same airline exists with departure time T’ = T + 7 days (+/- 30 minutes tolerance).

Terminology

Route : Unique combination of origin, destination and departure date.
Flight : Concrete flight scheduled per airline. Flights are in many-to-one relationship with routes.
Subscription : Origin/destination pair an agency is interested in.

Input

You will be provided with the sample data set consisting of three CSV files with following structure:

routes.csv	flights.csv	subscriptions.csv
route_id	flight_id	agency_id
origin_city_id	route_id	origin_city_id
destination_city_id	departure_time	destination_city_id
departure_date	arrival_time
	airline_id

The data set intentionally omits city, airline and agency tables, because they’re not crucial for the implementation of the algorithm.

Deliverables

Create a database with table structure to accommodate provided data and import the data into database tables as it is (no transformation needed – foreign keys already match).
Implement a data access layer (preferably using Entity Framework).
Implement a .NET console application taking three command line parameters:
- start date (in yyyy-mm-dd format)
- end date (in yyyy-mm-dd format)
- agency id (used to filter the flights an agency is interested in, by applying subscriptions)
```
   Example call: YourProgram.exe 2018-01-01 2018-01-15 1
```
Output the results in results.csv file, containing following columns: - flight_id
- origin_city_id
- destination_city_id
- departure_time
- arrival_time
- airline_id
- status (New / Discontinued)
Display execution metrics (i.e. time taken to execute the change detection algorithm).

Elaborate

Database design (data types, keys, indexes)
Overall structure of the application (layers, data flow, dependencies, (de)coupling) - Data access layer implementation
Change detection algorithm implementation
Data structures used
Optimizations applied

mahyarmoghadam / Zekju