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Solve 2024 day 22 part 2

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src
- main/scala/eu/sim642/adventofcode2024
  - Day22.scala
- test/scala/eu/sim642/adventofcode2024
  - Day22Test.scala

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Original file line number	Diff line number	Diff line change
`@@ -21,11 +21,32 @@ object Day22 {`
`21`	`21`	`def sumSecretsAfter(secrets: Seq[Secret], after: Int = 2000): Secret =`
`22`	`22`	`secrets.map(secretAfter(_, after)).sum`
`23`	`23`
	`24`	`+ def mostBananas(secrets: Seq[Secret]): Int = {`
	`25`	`+ // TODO: optimize (~4.7s)`
	`26`	`+ val secretMaps = secrets`
	`27`	`+ .map({ initialSecret =>`
	`28`	`+ Iterator.iterate(initialSecret, 2000 + 1)(nextSecret)`
	`29`	`+ .map(_ % 10)`
	`30`	`+ .map(_.toInt)`
	`31`	`+ .sliding(5)`
	`32`	`+ .map({ prices =>`
	`33`	`+ val changes = (prices lazyZip prices.tail).map((a, b) => b - a)`
	`34`	`+ changes -> prices.last`
	`35`	`+ })`
	`36`	`+ .groupMapReduce(_._1)(_._2)((a, _) => a)`
	`37`	`+ })`
	`38`	`+ val secretMaps2 = secretMaps`
	`39`	`+ .flatten`
	`40`	`+ .groupMapReduce(_._1)(_._2)(_ + _)`
	`41`	`+ secretMaps2.values.max`
	`42`	`+ }`
	`43`	`+`
`24`	`44`	`def parseSecrets(input: String): Seq[Secret] = input.linesIterator.map(_.toLong).toSeq`
`25`	`45`
`26`	`46`	`lazy val input: String = scala.io.Source.fromInputStream(getClass.getResourceAsStream("day22.txt")).mkString.trim`
`27`	`47`
`28`	`48`	`def main(args: Array[String]): Unit = {`
`29`	`49`	`println(sumSecretsAfter(parseSecrets(input)))`
	`50`	`+ println(mostBananas(parseSecrets(input)))`
`30`	`51`	`}`
`31`	`52`	`}`

Lines changed: 14 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -11,6 +11,12 @@ class Day22Test extends AnyFunSuite {`
`11`	`11`	`\|100`
`12`	`12`	`\|2024""".stripMargin`
`13`	`13`
	`14`	`+ val exampleInput2 =`
	`15`	`+ """1`
	`16`	`+ \|2`
	`17`	`+ \|3`
	`18`	`+ \|2024""".stripMargin`
	`19`	`+`
`14`	`20`	`test("Part 1 examples") {`
`15`	`21`	`assert(secretAfter(123, 1) == 15887950)`
`16`	`22`	`assert(secretAfter(123, 2) == 16495136)`
`@@ -28,4 +34,12 @@ class Day22Test extends AnyFunSuite {`
`28`	`34`	`test("Part 1 input answer") {`
`29`	`35`	`assert(sumSecretsAfter(parseSecrets(input)) == 21147129593L)`
`30`	`36`	`}`
	`37`	`+`
	`38`	`+ test("Part 2 examples") {`
	`39`	`+ assert(mostBananas(parseSecrets(exampleInput2)) == 23)`
	`40`	`+ }`
	`41`	`+`
	`42`	`+ test("Part 2 input answer") {`
	`43`	`+ assert(mostBananas(parseSecrets(input)) == 2445)`
	`44`	`+ }`
`31`	`45`	`}`

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