Oxygen System

Advent of Code 2019 Day 15

Try the simulator using your puzzle input!

Task: Solve for X where...

Part 1

X = the fewest number of movement commands required to move the repair droid from its starting position to the location of the oxygen system

Part 2

X = the number of minutes it will take to fill the space with oxygen

No example input

• Instead, several example input instructions and resulting output commands are simulated

Part 1

1. Intcode computer: Round 7!
2. Forget the algorithm: straight to building a simulator
3. The simulator revealed the path!
4. I painstakingly counted, and got the correct answer

Intcode computer: Round 7!

• Similar to Round 5 (Day 11), I must move a robot
• Unlike Round 5, the robot's path depends on my instructions, not just the state of the ground upon which it stands

Input rules:

Only four movement commands are understood: north (1), south (2), west (3), and east (4)

Output rules:

• A single output: one of 0,1,2
• 0: Wall. Didn't move.
• 1: Open. Moved.
• 2: Moved. At oxygen system!

Mission:

Direct the repair droid to the oxygen system and fix the problem

Forget the algorithm: straight to building a simulator

• I have no idea how I would algorithmically solve this puzzle
• But I do know how to build a simulator where I can listen for the next direction, run the program until it outputs another value, and update the robot's position and state of the area based on the status code

Off I go to try. Be back soon!

Ok, I'm back!

The simulator revealed the path!

• I built the simulator assuming a 50x50 square area, with the droid starting in the middle
• Just like in the instructions, I replace the contents of a cell with the correct object based on the status code returned after each attempted move
• I mapped each keyboard arrow key to the four input directions to make it delightfully interactive

Here's an animation of how the simulator revealed the path

I painstakingly counted, and got the correct answer

After some back-tracking to identify all the walls, I had what I needed to count the minimum steps necessary:

Here's a closer look at the shortest path:

Part 2

1. Forget the algorithm: I'll make a GIF!
2. To my delight, it was the correct answer!

Forget the algorithm: I'll make a GIF!

• 313 frames
• Each crafted individually
• Using letters from the alphabet to keep myself on track

It runs in about as many seconds as the hours it took to create:

To my delight, it was the correct answer!

• I'm so glad I used the alphabet and named my frames to match the number of minutes I was on

I did it!!!

• I solved both parts!
• I created my most complex GIF thus far in the series...and thankfully got the correct answer out of the tedious exercise!
• I built an interactive robot-maze-traversing simulator that helped me reveal the full maze, including the location of the oxygen system
• I've now completed 7/7 Intcode puzzles
• I've now built 7 Intcode computer simulators

The goal is always to solve, not necessarily with an algorithm.

And in my opinion, building a game is always a great way to solve these puzzles!