day7_1.nim

import strutils
from algorithm import nextPermutation
from sequtils import map

let initialTape = readLine(stdin).split(",").map(parseInt)

proc runAmp(firmware: seq[int], inputs: seq[int]): seq[int] =
  var tape = firmware
  var inputPos = 0
  var pos = 0
  while true:
    var codelen: int
    let instr = tape[pos]
    let opcode = instr mod 100
    let p1mode = (instr div 100) mod 10
    let p2mode = (instr div 1000) mod 10
    # let p3mode = (instr div 10000) mod 10
    case opcode:
      # Add
      of 1:
        codelen = 4
        let p1 = if p1mode == 0: tape[pos+1] else: pos+1
        let p2 = if p2mode == 0: tape[pos+2] else: pos+2
        tape[tape[pos+3]] = tape[p1] + tape[p2]
      # Multiply
      of 2:
        codelen = 4
        let p1 = if p1mode == 0: tape[pos+1] else: pos+1
        let p2 = if p2mode == 0: tape[pos+2] else: pos+2
        tape[tape[pos+3]] = tape[p1] * tape[p2]
      # Input
      of 3:
        codelen = 2
        let value = inputs[inputPos]
        tape[tape[pos+1]] = value
        inputPos += 1
      # Output
      of 4:
        codelen = 2
        let p1 = if p1mode == 0: tape[pos+1] else: pos+1
        result.add(tape[p1])
      # Jump if true
      of 5:
        codelen = 3
        let p1 = if p1mode == 0: tape[pos+1] else: pos+1
        let p2 = if p2mode == 0: tape[pos+2] else: pos+2
        if tape[p1] > 0:
          codelen = 0
          pos = tape[p2]
      # Jump if false
      of 6:
        codelen = 3
        let p1 = if p1mode == 0: tape[pos+1] else: pos+1
        let p2 = if p2mode == 0: tape[pos+2] else: pos+2
        if tape[p1] == 0:
          codelen = 0
          pos = tape[p2]
      # Less than
      of 7:
        codelen = 4
        let p1 = if p1mode == 0: tape[pos+1] else: pos+1
        let p2 = if p2mode == 0: tape[pos+2] else: pos+2
        if tape[p1] < tape[p2]:
          tape[tape[pos+3]] = 1
        else:
          tape[tape[pos+3]] = 0
      # Equals
      of 8:
        codelen = 4
        let p1 = if p1mode == 0: tape[pos+1] else: pos+1
        let p2 = if p2mode == 0: tape[pos+2] else: pos+2
        if tape[p1] == tape[p2]:
          tape[tape[pos+3]] = 1
        else:
          tape[tape[pos+3]] = 0
      # Halt
      of 99:
        break
      else:
        echo("You done goofed at pos " & $pos)
        break

    if codelen > 0:
      pos += codelen

var phases = @[0, 1, 2, 3, 4]
var thrusters = 0
while phases.nextPermutation():
  var output = 0
  for i in 0..<phases.len:
    let inputs = @[phases[i], output]
    output = runAmp(initialTape, inputs)[0]
  if output > thrusters:
    thrusters = output

echo("Max thrusters: " & $thrusters)