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