Day 11 part 1

const ROUNDS = 20

type
  Monkey = ref object
    items: seq[Natural]
    riskOp: proc(risk: Natural): Natural
    divisor, passTrue, passFalse, inspectCount: Natural

var
  monkeys = newSeq[Monkey]()
  answer: Natural

proc inspectItems(m: var Monkey) =
  m.items.apply(m.riskOp)
  for item in m.items:
    m.inspectCount.inc
    let targetMonkey = if item mod m.divisor == 0: m.passTrue else: m.passFalse
    monkeys[targetMonkey].items.add item
  m.items = @[]

proc newMonkey(s: string): Monkey =
  result = Monkey()
  var attrs = s.splitLines
  while attrs.len > 0:
    var a = attrs.pop.split(':')
    case a[0]
    of "  Starting items":
      a[1] = a[1].replace(" ", "")
      for i in a[1].split(','): result.items.add i.parseInt
    of "  Operation":
      let parsed = a[1].rsplit(' ', 2)
      if parsed[1] == "*" and parsed[2] == "old":
        result.riskOp = proc(risk: Natural): Natural = risk * risk div 3
      elif parsed[1] == "*":
        result.riskOp = proc(risk: Natural): Natural = 
          (risk * parsed[2].parseInt) div 3
      elif parsed[1] == "+" and parsed[2] == "old":
        result.riskOp = proc(risk: Natural): Natural = 2 * risk div 3
      elif parsed[1] == "+":
        result.riskOp = proc(risk: Natural): Natural = 
          (risk + parsed[2].parseInt) div 3
    of "  Test":
      result.divisor = a[1].rsplit(' ', 1)[1].parseInt
    of "    If true":
      result.passTrue = a[1].rsplit(' ', 1)[1].parseInt
    of "    If false":
      result.passFalse = a[1].rsplit(' ', 1)[1].parseInt
    else: discard

for m in "input.txt".readFile().split("\n\n"):
  monkeys.add newMonkey(m)

for _ in 0..<ROUNDS:
  for i in 0..<monkeys.len:
    if monkeys[i].items.len > 0: monkeys[i].inspectItems()

var inspectCounts = newSeq[Natural](monkeys.len)
for i in 0..<monkeys.len: inspectCounts[i] = monkeys[i].inspectCount
inspectCounts.sort(Descending)
answer = inspectCounts[0] * inspectCounts[1]

Answer is: 57348