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2024 Day 14 Part 2 - sort of

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Adam Millerchip 2024-12-14 17:47:15 +09:00
parent 5d3432ab87
commit 83d6f89769
1 changed files with 66 additions and 1 deletions
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67
2024/day14.exs
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@ -21,7 +21,72 @@ defmodule Day14 do
end
def part2({robots, size_x, size_y}) do
:not_done_yet
# The tree looks like this
# XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
# X X
# X X
# X X
# X X
# X X X
# X XXX X
# X XXXXX X
# X XXXXXXX X
# X XXXXXXXXX X
# X XXXXX X
# X XXXXXXX X
# X XXXXXXXXX X
# X XXXXXXXXXXX X
# X XXXXXXXXXXXXX X
# X XXXXXXXXX X
# X XXXXXXXXXXX X
# X XXXXXXXXXXXXX X
# X XXXXXXXXXXXXXXX X
# X XXXXXXXXXXXXXXXXX X
# X XXXXXXXXXXXXX X
# X XXXXXXXXXXXXXXX X
# X XXXXXXXXXXXXXXXXX X
# X XXXXXXXXXXXXXXXXXXX X
# X XXXXXXXXXXXXXXXXXXXXX X
# X XXX X
# X XXX X
# X XXX X
# X X
# X X
# X X
# X X
# XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
# Could improve this by searching for that pattern explicitly. In this case I just searched
# manually: noticed things looked suspicious after 27 seconds
# also noticed that repeated every 101 seconds
# Checked each 101 second jump until found the above tree
tick_forever(robots, size_x, size_y)
end
def tick_forever(robots, size_x, size_y, count \\ 27, acc \\ 27) do
robots = tick(robots, size_x, size_y, count)
robomap = MapSet.new(robots, fn [x, y, _, _] -> {x, y} end)
for y <- 0..(size_y - 1) do
for x <- 0..(size_x - 1) do
if MapSet.member?(robomap, {x, y}) do
IO.write("X")
else
IO.write(" ")
end
end
IO.puts("|")
end
IO.gets("#{acc} tree?")
tick_forever(robots, size_x, size_y, 101, acc + 101)
end
def tick(robots, size_x, size_y, times) do
Enum.map(robots, fn [px, py, vx, vy] ->
[Integer.mod(px + vx * times, size_x), Integer.mod(py + vy * times, size_y), vx, vy]
end)
end
def input do