aoc2025/day04/Notes.md

Day 4: Notes

Star 1

• cellular automata
• Moore neighborhood n
• each cell is initially in state s EMPTY OR FILLED
• counter i counts taken cells
• FILLED cell c gets accessible (becomes EMPTY) iff n(c) < 4
  • s'(c) := EMPTY
  • i' := i + 1
• Does grid keep frozen during checks? Aka is cell x+1 dependent on cell x?
• 2D grid array should be (x+2, y+2) instead of (x, y) so that edges don't go out of bounds, with first and last rows/columns being empty

Star 2

• cellular automata that refreshes and runs multiple times, until no more updates occur
• Bonus: Visualization using Ebitengine?