day8.rb

day8.rb

input = File.readlines('inputs/day8.in')

REGISTERS = Hash.new {|h,k| h[k] = Register.new(k, 0,0)}

class Register < Struct.new(:name, :value, :highest_value); end

class Condition < Struct.new(:register, :condition, :value)
  def check
    case condition
    when ">"
      register.value > value
    when "=="
      register.value == value
    when "<"
      register.value < value
    when "!="
      register.value != value
    when ">="
      register.value >= value
    when "<="
      register.value <= value
    end
  end
end

class Op < Struct.new(:amount, :condition)
  def perform(register)
    if condition.check
      operation(register)
      register.highest_value = [register.value, register.highest_value].max
    end
  end
end
class Increment < Op
  def operation(register)
    register.value += self.amount
  end
end

class Decrement < Op
  def operation(register)
    register.value -= self.amount
  end
end

input.each do |line|
  line =~ /^(\w+) (inc|dec) (-?\d+) if (\w+) (.+) (-?\d+)$/
  condition = Condition.new(REGISTERS[$4], $5, $6.to_i)
  operation_class = $2 == "inc" ? Increment : Decrement
  operation = operation_class.new($3.to_i, condition)
  operation.perform(REGISTERS[$1])
end
puts "max value: #{REGISTERS.values.map(&:value).max}"
puts "max value during execution: #{REGISTERS.values.map(&:highest_value).max}"