71 lines
2.0 KiB
Scala
71 lines
2.0 KiB
Scala
package aoc.y2017
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import aoc._
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object Day03 extends Day {
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override def part1(input: String): String = {
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val inum = input.toInt
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(inum match {
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case 1 => 0
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case _ =>
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val layer = (Math.sqrt(inum).ceil / 2).floor.toInt
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val square = ((layer + 1) * 2) - 1
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val diff = (square * square) - inum
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val wave = Math.abs(layer - (diff % (layer * 2)))
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layer + wave
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}).toString
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}
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override def part2(input: String): String = {
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sealed trait Direction {
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def change: (Int, Int)
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}
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case object MoveUp extends Direction {
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override def change: (Int, Int) = (0, 1)
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}
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case object MoveRight extends Direction {
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override def change: (Int, Int) = (1, 0)
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}
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case object MoveDown extends Direction {
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override def change: (Int, Int) = (0, -1)
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}
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case object MoveLeft extends Direction {
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override def change: (Int, Int) = (-1, 0)
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}
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def sumOfSurrounding(p: (Int, Int), m: Map[(Int, Int), Int]): Int = {
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val surrounding = List(
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(-1, 1),
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(0, 1),
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(1, 1),
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(-1, 0),
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(1, 0),
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(-1, -1),
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(0, -1),
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(1, -1)
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)
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surrounding.map(o => m.getOrElse(p + o, 0)).sum
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}
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lazy val movementStream: Stream[Int] = Stream.from(1).flatMap(i => Stream(i, i))
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lazy val directionStream: Stream[Direction] = MoveRight #:: MoveUp #:: MoveLeft #:: MoveDown #:: directionStream
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lazy val pathStream = movementStream.zip(directionStream).flatMap {
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case (times, dir) => Stream.fill(times)(dir)
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}
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lazy val pathIterator = pathStream.toIterator
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val targetNum = input.toInt
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def findNext(m: Map[(Int, Int), Int] = Map((0, 0) -> 1), p: (Int, Int) = (0, 0), i: Iterator[Direction]): Int = {
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val nd = i.next()
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val np = p + nd.change
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val sum = sumOfSurrounding(np, m)
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val nm = m + (np -> sum)
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if (sum > targetNum) {
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sum
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} else {
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findNext(nm, np, i)
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}
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}
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findNext(i = pathIterator).toString
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}
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}
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