laithshadeed / nasa-explorer-app

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Nasa Explorer App Puzzle (2016)

This is work-in-progress sample code while learning Ruby. This problem is quite interesting because you can solve it in many ways. I provided here two sample codes. Short one (my preferred) in exec/no_oop and long one (oop) in exec/nasa_explorer_app. I added description in each file. For the OOP solution, it is over-engineered. I was trying to revisit basic concepts like: linked lists, queues, graph, breadth-first traversal, composition, dynamic dispatch.

Here the problem statement

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
lower-left 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

Testt Input:

5 5

1 2 N

LMLMLMLMM

3 3 E

MMRMMRMRRM

Expected Output:

1 3 N

5 1 E

Try

Execute:

$ ./exe/nasa_explorer_app sample_data.txt
$ ./exe/no_oop sample_data.txt

Unit tests:

$ rspec

Rubocop

$ rubocop

My other code samples in other languages

  • Feedback UI in Angular (JS) (2015)
  • Twitter timeline (PHP) (2014)
  • In-memory filesystem (C++) (2012)
  • Log parser (C++) (2011)
  • Expression tree (Java) (2010)

License

The gem is available as open source under the terms of the MIT License.

About

License:MIT License


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