Solutions in Kotlin!
My solutions to the ingenious Advent Of Code 2019 by Eric Wastl.
I am doing these challenges for the third year in a row now and I am totally addicted to them. If you are into programming, into logic, maybe also a little bit into competition, this one is for you as well!
| Day | Title | Remarks |
|---|---|---|
| 1 | The Tyranny of the Rocket Equation | As usual, solvable with Excel in a matter of minutes. :) |
| 2 | 1202 Program Alarm | Our IntProgram running ship computer comes to life with a few instructions! |
| 3 | Crossed Wires | Tangled wires with directional instructions need to be parsed for crossings. The first puzzle that demands some visualization! |
| 4 | Secure Container | Definition of a valid password and your task to scan a range of numbers for just the valid ones. Can be used to create ultra optimized solutions! |
| 5 | Sunny with a Chance of Asteroids | Extending day 2's rudimentary ship computer once more to include new instructions for in/out, immediate mode and comparision & jumps |
| 6 | Universal Orbit Map | Definitions of objects in space and their orbits make you order them up and find optimized orbital paths. |
| 7 | Amplification Circuit | Taking the ship computer to the next level by hooking some of them up together. Now in/out has to be connected somehow. |
| 8 | Space Image Format | A sequence of digits represent a layered monochrome image that has to be decrypted and displayed. Fun. |
As usual, we get into things with a little entry-level coding warm-up. The first part is pure math. All that is interesting here to note, is that "rounding down" is the default in integer arithmetic, so no special treatment is needed. My favorite approach, as usual, is a functional way to state:
"Sum up all elements after applying this function":
moduleMasses.sumBy { it.fuelForMass }
Part 2 requires a little recursion to keep track of how much more fuel is needed to carry the fuel you just calculated itself. Straight forward.
Exceptionally early this year we hit the very first simple CPU emulation! It's a ship computer running Intcode programs. Well essentially all CPUs run code that is nothing more than numbers.
The trick here - and sadly something that cost me several minutes this morning -
was to really make sure the indirect memory addressing works flawlessly.
Other than that, I spent some time this afternoon to refactor and build a ShipComputer
class, ready for extensions in the upcoming puzzles!
Huray! Today's puzzle brought the first opportunity to go fancy with a graphical visualization of the matter!
But let's start with the problem. It's a "find common points of wires in 2D space and find a point/coordinate that meets some criteria"
So, following the given directional sequence of the wire layouts, one way to approach this is to first trace each and every point that is ever touched by a wire and then do an intersection of the two sets of points to find only the common points.
val commonPoints = wirePoints[0].intersect(wirePoints[1])
To further get the required single point, Kotlin again comes with easy to use
functions on arbitrary data: minBy is your friend!
Furthermore, this puzzle led me to typealias a tuple (Pair in Kotlin) to a
Point along with helpful extension properties and functions tailored for it like:
val Point.x: Int
get() = first
val Point.y: Int
get() = second
val Point.manhattanDistance: Int
get() = x.absoluteValue + y.absoluteValue
For the graphical show-off I enjoyed using my new PixelGameEngine, inspired by the very cool C++ olcPixelGameEngine!
You'll find a Day03Graphical.kt file that uses my new primitive engine as a support to easily draw some lines (the wires) along with their respective common points. Check it out!