79 lines
1.4 KiB
Crystal
79 lines
1.4 KiB
Crystal
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require "advent"
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INPUT = input(2020, 24).lines.map &.tiles.map { |t| MATCHES[t] }
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MATCHES = { "se" => {0.5, -1.0}, "sw" => {-0.5, -1.0}, "ne" => {0.5, 1.0}, "nw" => {-0.5, 1.0}, "e" => {1.0, 0.0}, "w" => {-1.0, 0.0} }
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class String
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def tiles
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i = 0
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tiles = [] of String
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while i < size
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if self[i] == 's' || self[i] == 'n'
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tiles << self[i..i+1]
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i += 2
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else
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tiles << self[i..i]
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i += 1
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end
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end
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tiles
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end
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end
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class Array(T)
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def pos
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curr = {0.0, 0.0}
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each do |c|
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curr = curr.add c
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end
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curr
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end
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end
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def part1(input)
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counts = Hash({Float64,Float64}, Int32).new(0)
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input.each do |i|
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counts[i.pos] += 1
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end
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counts.count &.[1].%(2).==(1)
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end
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struct Tuple(*T)
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def neighbors
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MATCHES.values.map &.add(self)
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end
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end
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def part2(input)
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state = Hash({Float64,Float64}, Bool).new(false)
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counts = Hash({Float64,Float64}, Int32).new(0)
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input.each do |i|
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state[i.pos] ^= true
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end
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100.times do |i|
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counts.clear
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state.each do |t, f|
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next unless f
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t.neighbors.each do |n|
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counts[n] += 1
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end
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end
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new_state = state.clone.clear
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state.each do |k, v|
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next unless v
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new_state[k] = !(counts[k] == 0 || (counts[k] > 2))
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end
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counts.each do |k, v|
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new_state[k] = true if (!state[k]) && v == 2
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end
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state = new_state
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end
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state.count &.[1]
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end
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puts part1(INPUT.clone)
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puts part2(INPUT.clone)
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