murray-tait/aquila-interview

aquila-interview

Developer Interview Exercise

Task

Write a Java program that outputs a count of all the legal phone numbers that can be generated by moving a chess piece around a standard telephone keypad.

A legal phone number has the following requirements:

• Must be 10 digits long.
• Must contain only digits (no * or #).

The telephone keypad layout is:

1 2 3
4 5 6
7 8 9
* 0 #

The program must take its input from the command line, accepting:

• The name of a chess piece (king, queen, bishop, knight, rook, pawn).
• A starting digit, 0 to 9.

For example, java ChessPhoneNumbers queen 5

The program should not return a list of the actual numbers generated; just the count of them.

A legal move is defined as any move that is normally legal for the piece in chess, with the following additions:

• Staying in place is a legal move for all pieces.
• When a pawn reaches the top row, it becomes a queen.

A pawn, starting on one of the bottom two rows (one of the digits 7, 8, 9 or 0), may move either one or two spaces forward the first time it moves .

Prerequisites

Install Java JDK 8

The source code comes with Maven wrapper, therefore a separate Maven installation is not required.

Launching the program

Execute java -jar target/aquila-interview-0.1.0-SNAPSHOT.jar queen 5 to run the program with a Queen starting on the 5 key.

This should return 963635092 as a count of the number of legal phone numbers.

Building

Execute mvnw.cmd clean package (Windows) or ./mvnw clean package (Linux and MacOS) to build, run tests, and create jars.