Moon Robot

While studying backend development at uni in 2024, we were given a simple task for our first assignment, with an option for a single bonus mark for making our solutions as short as possible (without just "cheating" by putting it all on one line).

Most assignments were generally pretty boilerplate, so even doing a good job of them resulted in something that I usually didn't think was anything special, even in cases where my submission was marked highly.

This is one of the few things I ever made in the course of completing uni assignments that I thought was actually of some interest independent of an academic environment.

You need to run the program with command line arguments. If debugging with Visual Studio you can make use of command line arguments using these instructions.

Task sheet

General Instructions

Your task is to implement a Proof of Concept (POC) of the Moon robot simulation. The surface of Moon can be presented as a square grid of the size N.

You need to create a console application that will simulate a Moon robot moving on a square map of dimensions N x N. There are no other obstacles on the map. The robot is free to wander around the surface of the Moon, but must be prevented from falling off the map. Any movement that would result in the robot falling from the table must be ignored by the robot. However, further valid direction commands must still be permitted. Robot should remain operable while on the map.

Application Specification

Supported Robot Commands

Here is a list of supported direction commands that should be implemented in the POC.

Command	Description
PLACE X,Y,D	the robot on the map at coordinate (X,Y) facing the cardinal direction D out of 4 possible directions: NORTH, EAST, SOUTH, WEST
LEFT	Turn the robot 90 degrees LEFT without changing its coordinates.
RIGHT	Turn the robot 90 degrees RIGHT without changing its coordinates.
MOVE	Move robot one coordinate in the direction that it's facing.

Constraints

1. The robot must ignore all commands until it is dropped on the map. E.g. The robot must not move or turn until it is placed on the map.
2. The robot must not perform any invalid moves. E.g. fall off the map.
3. The map must be not smaller than 2x2 and no larger than 100x100 squares.
4. The map must be square. E.g. 25x25, but not 10x50.

Technology Stack Requirements

The application must be cross-platfrom and be able to run from the terminal. Please use the latest version of dotnet to create a new console application and use your IDE of choice to accomplish the task.

Original solution (9 lines, 1,570 characters)

I originally submitted a 9-line solution and moved on to other things for the rest of the semester. I believed I could do better but the extra credit was a single mark so it wasn't academically efficient to continue working on it.

This solution was the result of two basic ideas: the conditions were merely complicated functions (abc inputs mapped to xyz outputs deterministically) and the idea of "cheating" by using the equivalent of a dictionary lookup -- via hashing -- as I'd learnt about Big O in an earlier unit on data structures.

The "skeleton" of this solution is:

var = value;
var;
while (conditions)
{
    if (conditions) var = value;                                    // handle PLACE command
    if (conditions) var = value; else if (conditions) var = value;  // handle LEFT and RIGHT commands
    if (conditions) var = value; else if (conditions) var = value;  // handle MOVE (west) and MOVE (north) commands
    if (conditions) var = value; else if (conditions) var = value;  // handle MOVE (east) and MOVE (south) commands
}

Later on we were encouraged to record a video explaining our solutions. I've uploaded that original 2024 video: YouTube.

Revised Solution (6 lines, 2,765 characters)

Towards the end of the semester I got a brain worm about how it should be possible to build on the ideas in my original implementation to further condense it down, so opted to take a few days off of the assignments that were an academic priority to have another stab at condensing my solution further.

The main difference is combining the processing of the LEFT, RIGHT, and MOVE commands into a single line.

I also used a self-imposed constraint of avoiding the use of ternary operators and any conditional check (on one line) that involved more than an if-else; ideally even an if-else would not be allowed on one line.

The "skeleton" of my revised solution is:

var = value;
while (conditions)
{
    if (conditions) var = value;    // handle PLACE command (copied from original)
    if (conditions) var = value;    // handle LEFT, RIGHT, and MOVE (all directions) commands 
}

Upon completing this implementation I believed it should be possible to combine both assignments into one line of code from hell, but I had already spent more time than was academically advisable so did not seriously attempt to do so.

As with the original, I recorded a video to coincide with my revised solution. I've uploaded that original 2024 video: YouTube.

License

• Code and documentation are licensed under the fuck around and find out license (fafol) v0.1 or later.