AoC 2022 Day 23: Elf Scattinator

Source: Unstable Diffusion

Part 1

Implement a cellular automaton with the following rules:

  • If you have no neighbors, don’t move (important, I forgot this one for a while)
  • Otherwise:
    • Calculate a potential move:
      • If you have no neighbors to the north, move north
      • If not, check likewise for south, then west, than east
    • If no other agent is moving to the same space, move to your potential move
    • Otherwise, don’t move
  • On each frame, rotate the order the directions are checked in (NSWE, SWEN, WENS, ENSW, NSWE, …)


AoC 2022 Day 22: Wonderator

Source: Monkey Map

Part 1

Given a map and a series of instructions formatted as distance + turn (L or R), find the final position. Any time you would walk off the edge of the map, wrap to the opposite edge.


AoC 2017 Day 21: Fractal Expander

Source: Fractal Art

Part 1: Start with an input image made of . and # pixels. For n iterations, break the image into blocks:

  • If the current size is even, break the image into 2x2 chunks and replace each with a 3x3 chunk
  • If the current size is odd, break the image into 3x3 chunks and replace each with a 4x4 chunk

The replacement rules will be specified in the following format (example is a 3x3 -> 4x4 rule):

.#./..#/### => #..#/…./…./#..#

> In that example, replace this:

> ```

With this:

#..# …. …. #..#


AoC 2017 Day 18: Duetvm

Source: Duet

Part 1: Create a virtual machine with the following instruction set:

  • snd X plays a sound with a frequency equal to the value of X
  • set X Y sets register X to Y
  • add X Y set register X to X + Y
  • mul X Y sets register X to X * Y
  • mod X Y sets register X to X mod Y
  • rcv X recovers the frequency of the last sound played, if X is not zero
  • jgz X Y jumps with an offset of the value of Y, iff X is greater than zero

In most cases, X and Y can be either an integer value or a register.

What is the value recovered by rcv the first time X is non-zero?