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@ -1,39 +1,49 @@
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include Math
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include Math
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def follow_instructions(input)
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Instruction = Struct.new(:direction, :blocks) do
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seq = input.split(', ')
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def initialize(direction, blocks)
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super(direction, blocks.to_i)
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end
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end
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# start facing north at the origin
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Turtle = Struct.new(:orientation, :location) do
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dir = -PI/2
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def self.run(input)
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locations = [[0,0]]
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instructions = parse(input)
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seq.each.with_object(locations) do |step, locations|
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turtles = [Turtle.new(-PI/2, [0,0])]
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/(?<turn>\w)(?<blocks>\d+)/ =~ step
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case turn
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instructions.each.with_object(turtles) do |instruction, turtles|
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when ?R
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turtles << turtles.last.turn(instruction.direction).step
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dir += PI/2
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(instruction.blocks - 1).times do
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when ?L
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turtles << turtles.last.step
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dir -= PI/2
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end
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else
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raise "unexpected turn: #{turn}"
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end
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end
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blocks.to_i.times do
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turtles
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location = locations.last
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x = location[0] + cos(dir).to_i
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y = location[1] + sin(dir).to_i
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locations << [x, y]
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end
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end
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def self.parse(input)
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input.split(', ').map {|step|
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Instruction.new(*step.scan(/(?<turn>\w)(?<blocks>\d+)/)[0])
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}
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end
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end
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locations
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def turn(direction)
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end
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angle = case direction
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when ?R
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PI/2
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when ?L
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-PI/2
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else
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raise "unexpected direction: #{direction}"
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end
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Turtle.new(orientation + angle, location)
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end
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def first_dupe(ary)
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def step
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seen = Set.new
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x = location[0] + cos(orientation).to_i
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ary.find { |elem|
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y = location[1] + sin(orientation).to_i
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seen.include?(elem) || (seen << elem && false)
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Turtle.new(orientation, [x, y])
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}
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end
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end
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end
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require 'minitest'
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require 'minitest'
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@ -45,23 +55,17 @@ class TestInstructions < Minitest::Test
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assert_distance 12, 'R5, L5, R5, R3'
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assert_distance 12, 'R5, L5, R5, R3'
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end
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end
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def test_first_dupe
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assert_equal 1, first_dupe([1, 2, 3, 1])
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assert_equal 2, first_dupe([1, 2, 3, 2])
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assert_equal 3, first_dupe([1, 2, 3, 3])
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locations = follow_instructions('R8, R4, R4, R8')
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assert_equal [4, 0], first_dupe(locations)
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end
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def assert_distance(expected, instructions)
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def assert_distance(expected, instructions)
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locations = follow_instructions(instructions)
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assert_equal expected, Turtle.run(instructions).last.location.map(&:abs).inject(:+)
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assert_equal expected, locations.last.map(&:abs).inject(:+)
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end
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end
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end
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end
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if __FILE__ == $0
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if __FILE__ == $0
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puts first_dupe(follow_instructions(DATA.read))
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turtles = Turtle.run(DATA.read)
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p turtles.last
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locations = turtles.map(&:location)
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p locations.find {|location| locations.count(location) > 1 }
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end
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end
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__END__
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__END__
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