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#!/usr/bin/env ruby
class Machine
def initialize(starting_memory = [])
@mem = starting_memory
@pc = 0
@halt = false
@buffered_input = []
@buffered_output = []
@relative_base = 0
end
def mem(start = 0, len = @mem.length)
@mem[start...(start + len)]
end
def halt!
@halt = true
end
def halt?
@halt
end
def buffer_input(x)
if x.is_a?(Array) then
@buffered_input += x
else
@buffered_input.push(x)
end
end
def buffered_output(flush = false)
t = @buffered_output
@buffered_output = [] if flush
t
end
def step
return if halt?
opcode = @mem[@pc] % 100
if opcode == 99 then
halt!
@pc += 1
return
end
p3, p2, p1 = ("%03d" % (@mem[@pc] / 100)).chars
l1w, l1r = get(p1, 1)
l2w, l2r = get(p2, 2) if [1,2,5,6,7,8].include?(opcode)
l3w, l3r = get(p3, 3) if [1,2,7,8].include?(opcode)
case opcode
when 1
@mem[l3w] = l1r + l2r
@pc += 4
when 2
@mem[l3w] = l1r * l2r
@pc += 4
when 3
@mem[l1w] = @buffered_input.shift
@pc += 2
when 4
@buffered_output.push(l1r)
@pc += 2
when 5
@pc = (l1r != 0 ? l2r : @pc + 3)
when 6
@pc = (l1r == 0 ? l2r : @pc + 3)
when 7
@mem[l3w] = (l1r < l2r ? 1 : 0)
@pc += 4
when 8
@mem[l3w] = (l1r == l2r ? 1 : 0)
@pc += 4
when 9
@relative_base += l1r
@pc += 2
end
end
def run
until halt? do
step
end
end
private
def get(p, a)
w = case p
when "0"
@mem[@pc + a]
when "2"
@relative_base + @mem[@pc + a]
end
r = case p
when "0"
@mem[@mem[@pc + a]]
when "1"
@mem[@pc + a]
when "2"
@mem[@relative_base + @mem[@pc + a]]
end
[w, r || 0]
end
end
input = $stdin.readlines[0].strip.split(",").map(&:to_i)
input[0] = 2
m = Machine.new(input)
istr = <<-EOS
A,B,A,C,B,A,C,B,A,C
L,12,L,12,L,6,L,6
R,8,R,4,L,12
L,12,L,6,R,12,R,8
n
EOS
m.buffer_input(istr.chars.map(&:ord))
m.run
puts m.buffered_output.last
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