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#!/usr/bin/env ruby
class Firewall
class Layer
attr_reader :range
def initialize(range)
@scanner_location = 0
@scanner_velocity = 1
@range = range
end
def move_scanner!
if @scanner_location == (@range - 1) then
@scanner_velocity = -1
elsif @scanner_location == 0 then
@scanner_velocity = 1
end
@scanner_location += @scanner_velocity
end
def capturing?
return @scanner_location == 0
end
end
def initialize
@layers = []
end
def add_layer!(depth, range)
@layers[depth] = Layer.new(range)
end
def total_depth
return @layers.length
end
def severity(loc)
return 0 if @layers[loc].nil?
return 0 unless @layers[loc].capturing?
return loc * @layers[loc].range
end
def tick!
@layers.compact.each(&:move_scanner!)
end
end
input = $stdin.readlines.map(&:chomp)
firewall = Firewall.new
input.each do |line|
depth, range = line.split(': ').map(&:to_i)
firewall.add_layer!(depth, range)
end
myloc = -1
total_severity = 0
while myloc < firewall.total_depth do
myloc += 1
total_severity += firewall.severity(myloc)
firewall.tick!
end
puts total_severity
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