initial state: #.......##.###.#.#..##..##..#.#.###..###..##.#.#..##....#####..##.#.....########....#....##.#..##...

..... => .

#.... => .

..### => .

##..# => #

.###. => #

...## => .

#.#.. => .

..##. => .

##.#. => #

..#.. => .

.#... => #

##.## => .

....# => .

.#.#. => .

#..#. => #

#.### => .

.##.# => #

.#### => .

.#..# => .

####. => #

#...# => #

.#.## => #

#..## => .

..#.# => #

#.##. => .

###.. => .

##### => #

###.# => #

...#. => #

#.#.# => #

.##.. => .

##... => #

initial state: #..#.#..##......###...###

...## => #

..#.. => #

.#... => #

.#.#. => #

.#.## => #

.##.. => #

.#### => #

#.#.# => #

#.### => #

##.#. => #

##.## => #

###.. => #

###.# => #

####. => #

package org.codefork.aoc2018

import scala.io.Source

object Day12Part1 extends Part {

def nextGen(state: String, pos: Int, rules: Map[String, String]) = {

val slice = state.substring(pos - 2, pos + 3)

val result =

if (rules.contains(slice))

rules(slice)

else "."

result

}

def trimTrailingPeriods(s: String) = s.reverse.dropWhile(_ == '.').reverse

override def answer: String = {

val url = getClass.getResource("/day12/input.txt")

val lines = Source.fromURL(url).getLines().toSeq

lines.head

.replace("initial state: ", "")

.zipWithIndex

.foldLeft(Set[Int]()) {

case (acc, (char, index)) => {

acc ++ (if (char == "#") Set(index) else Set.empty)

}

}

val initial = lines.head.replace("initial state: ", "")

val rules = lines

.drop(2)

.map(line => line.substring(0, 5) -> line.last.toString)

.toMap

val result = 1.to(20).foldLeft((0, initial)) { case ((startingPotNumberOfState, state), i) =>

{

val padded = "...." + state + "...."

// result of next gen will be have 4 slots than padded

val t1 = 2

.to(padded.size - 3)

.map(pos => {

nextGen(padded, pos, rules)

})

.mkString

val t2 = t1.dropWhile(ch => ch == '.')

val newStartingPotNumberOfState = startingPotNumberOfState - 2 + (t1.length - t2.length)

val t3 = trimTrailingPeriods(t2)

//println(i, (newStartingPotNumberOfState, t3))

(newStartingPotNumberOfState, t3)

}

}

val count = result._2.foldLeft((result._1, 0)) {

case ((potNumber, acc), char) => {

val newAcc = acc + (if (char == '#') potNumber else 0)

(potNumber + 1, newAcc)

}

}

count._2.toString

}

}