AdventOfCode-2022/day9.cr

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2022-12-08 22:19:40 -08:00
require "advent"
INPUT = input(2022, 9).lines.map do |line|
dir, n = line.split(" ");
{dir, n.to_i64}
end
positions = Set(Tuple(Int32, Int32)).new
diff = { "L" => {-1, 0}, "R" => {1, 0}, "U" => {0, 1}, "D" => {0, -1} }
def move(h, d)
{h[0] + d[0], h[1] + d[1]}
end
def follow(h, t)
hx, hy = h
tx, ty = t
dx = hx-tx
dy = hy-ty
if dx.abs > 1 && dy.abs == 0
tx += dx.sign
elsif dy.abs > 1 && dx.abs == 0
ty += dy.sign
elsif dx.abs + dy.abs > 2
tx += dx.sign
ty += dy.sign
end
h = {hx, hy}
t = {tx, ty}
return {h, t}
end
def simulate(knots, d)
knots[0] = move(knots[0], d)
(knots.size-1).times do |i|
knots[i], knots[i+1] = follow(knots[i], knots[i+1])
end
end
knots = [{0, 0}] * 10
INPUT.each do |cmd|
dir, n = cmd
d = diff[dir]
n.times do
simulate(knots, d)
positions << knots.last
end
end
puts positions.size