Mars Rover

Thoughtworks challenge in Graduate Program Recruitment

Brief Explanation

In this challenge I used JUnit library in order to make easier all test management. That is why I decided to convert the project to a maven project because it makes more comfortable to manage all dependencies.

I designed an OOP architecture for this project where we can find all de source code in main folder and all tests in test folder:

main
  java
    com
      thoughtworks
        MarsRover
          controller
            PlateauController.java
            PlateauControllerImpl.java
            RobotController.java
            RobotControllerImpl.java
          domain
            Plateau.java
            RoverRobot.java
          factory
            ServiceFactory.java
          service
            MarsRoverService.java
            MarsRoverServiceImpl.java
          Main.java

Controller

I created a controller for each domain model in order to control all the actions in relation with these items. I decided to create an interface for each controller because if we want to add a new behaviour in the future of this project, having an interface makes easier this issue.

• PlateauController.java: this controller manages all actions in relation with a Plateau, for example create an instance of a plateau.
• RobotController.java: this controller manages all actions in relation with a Robot, for example create an instance of a robot, check if it can move, make a movement or rotate.

Domain

I created a class for each model in this project with all parameters that they need.

• Plateau.java: this item has an x upper-right coordinate and a y upper-right coordinate.
• RoverRobot.java: this item has an x coordinate, y coordinate and an orientation.

Factory

I created a singleton class in order to restrict an only one instance of each service that we need in this project.

• ServiceFactory.java: this singleton class has a getXService() function for each X service that exists in this project.

Service

I created a service in order to group all the actions that some controllers have a relationship between them. I decided to create an interface for each service because if we want to add a new behaviour in the future of this project, having an interface makes easier this issue.

• MarsRoverService.java: this service groups PlateauController and RobotController in order to solve the Mars Rover problem.

Main

I created a Main class as start point to run this project.

• Main.java: this class has a main function that reads from command line, runs solve function of MarsRoverService and print the solution through also command line.

test
  java
    com
      thoughtworks
        MarsRover
          controller
            PlateauController.java
            RobotController.java
          domain
            Plateau.java
            RoverRobot.java
          factory
            ServiceFactory.java
          service
            MarsRoverService.java

I created a test class for each class in order to test the correct execution of their behaviour in all the possible situations, including input verification.

All classes and methods are documented in JavaDoc.

Run project

Needs: Java 6 & maven

Program

1. Extract files from MarsRoverAS.zip
2. cd MarsRoverAS/
3. mvn clean
4. mvn compile
5. mvn exec:java

Test

1. Extract files from MarsRoverAS.zip
2. cd MarsRoverAS/
3. mvn clean
4. mvn compile
5. mvn test

Problem

A squad of robotic rovers are to be landed by NASA on a plateau on Mars. This plateau, which is curiously rectangular, must be navigated by the rovers so that their on-board cameras can get a complete view of the surrounding terrain to send back to Earth.

A rover’s position and location is represented by a combination of x and y co-ordinates and a letter representing one of the four cardinal compass points. The plateau is divided up into a grid to simplify navigation. An example position might be 0, 0, N, which means the rover is in the bottom left corner and facing North.

In order to control a rover, NASA sends a simple string of letters. The possible letters are ‘L’, ‘R’ and ‘M’. ‘L’ and ‘R’ makes the rover spin 90 degrees left or right respectively, without moving from its current spot. ‘M’ means move forward one grid point, and maintain the same heading.

Assume that the square directly North from (x, y) is (x, y+1).

Input:

• The first line of input is the upper-right coordinates of the plateau, the lowerleft coordinates are assumed to be 0,0.
• The rest of the input is information pertaining to the rovers that have been deployed. Each rover has two lines of input. The first line gives the rover’s position, and the second line is a series of instructions telling the rover how to explore the plateau.
• The position is made up of two integers and a letter separated by spaces, corresponding to the x and y co-ordinates and the rover’s orientation.
• Each rover will be finished sequentially, which means that the second rover won’t start to move until the first one has finished moving.

Output:

• The output for each rover should be its final co-ordinates and heading.

Input and Output

Test Input: 5 5 1 2 N LMLMLMLMM 3 3 E MMRMMRMRRM

Expected Output: 1 3 N 5 1 E

Rules

1. Do not not use any external libraries to solve this problem, but you may use external libraries or tools for building or testing purposes. Specifically, you may and are encouraged to use unit-testing libraries and build tools available for your chosen language (e.g., JUnit, Ant, NUnit, Rspec, Rake, etc.)
2. System security is very important to us and certain file extensions will be blocked for security purposes, resulting in delays to your application. You should NOT include any executable attachments, including those with .exe or .lib extensions. Please submit your code as a zipped file of source code and supporting files, without any compiled code. If you're submitting in C#, please do not submit your code as a .msi file
3. Please include a brief explanation of your design and assumptions, along with your code, as well as detailed instructions to run your application
4. When submitting your code, please label it in the following manner: ExerciseLanguageYourInitials for example TrainsJavaMS
5. To assist us carrying out an unbiased review, please do not include your full name in the source code or Readme file
6. We want our hiring process to be fair, and for everyone to start from the same place. To enable this, we request that you do not share or publish these problems, or your solution
7. We assess a number of things including the design aspect of your solution and your object oriented or functional programming skills. While these are small problems, we expect you to submit what you believe is production-quality code; code that you’d be able to run, maintain, and evolve. You don’t need to gold plate your solution. We ask that you strive for simplicity, instead of an over–sophisticated solution
8. Please compress your files into a single .zip file before upload. Kindly ensure there are no executables in your submission. Our system blocks executable files* for security purposes, and we want to avoid any delays in your process
9. Executables include asp, bat, class, cmd, com, cpl, dll, exe, fon, hta, ini, ins, iw, jar, jsp, js, jse, pif, scr, shs, sh, vb, vbe, vbs, ws, wsc, wsf, wsh & msi

Notes

• For the solution, we request that you use Java, Ruby, C#, Python, Clojure, Scala or JavaScript.
• There must be a way to supply the application with the input data via text file
• We need to be able to build and run your code ourselves
• You should provide sufficient evidence that your solution is complete by indicating that it works correctly against the supplied test data
• Please use the URL at the bottom of this email to submit your code.
• We encourage candidates to include the code revision history (e.g. .git folder or .hg folder) in their submission to show their commits

Copyright 2012 ThoughtWorks, Inc