Advent of Code 25.scala

import java.io.FileInputStream
import collection.immutable.HashMap
import scala.annotation.tailrec
import scala.io.StdIn

def transforms(number: BigInt, subjectNumber: BigInt): BigInt = {
  number * subjectNumber % 20201227
}

def loopedTransforms(subjectNumber: BigInt, loop: Int, number: BigInt = 1): BigInt = {
  if 0 == loop then
    number
  else
    loopedTransforms(subjectNumber, loop - 1, transforms(number, subjectNumber))
}

def findLoop(subjectNumber: BigInt, target: BigInt, number: BigInt = 1, loop: Int = 0): Int = {
  if number == target then
    loop
  else
    findLoop(subjectNumber, target, transforms(number, subjectNumber), loop + 1)
}

def solve25_1(cardPublicKey: BigInt, doorPublicKey: BigInt): BigInt = {
  val cardLoopSize = findLoop(7, cardPublicKey)
  loopedTransforms(doorPublicKey, cardLoopSize)
}

@main def solve25() =
  val in = new FileInputStream("example25-1.in")
  System.setIn(in)

  val key1 = StdIn.readInt()
  val key2 = StdIn.readInt()
  println(solve25_1(key1, key2))