50 lines
1.5 KiB
Scala
50 lines
1.5 KiB
Scala
package tf.bug.aoc.y2020
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import cats.effect._
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import cats.parse.{Parser => P, Parser1, Numbers}
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import cats.syntax.all._
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import fs2._
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import tf.bug.aoc.Day
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object Day2 extends Day {
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case class Policy(min: Int, max: Int, letter: Char)
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case class Entry(policy: Policy, password: String)
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val parsePolicy: Parser1[Policy] =
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(Numbers.nonNegativeIntString, P.char('-'), Numbers.nonNegativeIntString, P.char(' '), P.anyChar).mapN {
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case (min, (), max, (), letter) =>
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Policy(min.toInt, max.toInt, letter)
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}
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val parseEntry: Parser1[Entry] =
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(parsePolicy, P.string1(": "), P.until1(P.end)).mapN {
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case (policy, (), password) =>
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Entry(policy, password)
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}
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override def part1[F[_]: Async]: Pipe[F, String, String] =
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parts[F] { ent =>
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val charCount = ent.password.count(_ == ent.policy.letter)
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ent.policy.min <= charCount && charCount <= ent.policy.max
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}
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override def part2[F[_]: Async]: Pipe[F, String, String] =
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parts[F] { ent =>
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val a = ent.policy.min <= ent.password.length && ent.password.charAt(ent.policy.min - 1) == ent.policy.letter
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val b = ent.policy.max <= ent.password.length && ent.password.charAt(ent.policy.max - 1) == ent.policy.letter
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(a || b) && !(a && b)
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}
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def parts[F[_]: Sync](validation: Entry => Boolean): Pipe[F, String, String] =
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(lines: Stream[F, String]) => {
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lines.map(parseEntry.parseAll)
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.collect {
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case Right(entry) => entry
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}
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.foldMap(ent => if(validation(ent)) 1 else 0)
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.map(_.show)
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}
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}
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