Adding day 4

day4/part1.scala

@@ -0,0 +1,64 @@
+import scala.io.StdIn.readLine
+import java.time.{LocalDate, LocalTime}
+import java.time.format.DateTimeFormatter
+
+val fmt: DateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd kk:mm")
+
+case class Entry(shiftDate: LocalDate, time: LocalTime, id: Option[Int], sleep: Option[Boolean])
+
+def parseEntry(input: String): Entry = {
+  "\\[([^\\]]+)\\] ([^ ]+) ([^ ]+)".r.findFirstMatchIn(input).map {
+    m => 
+      val ts = fmt.parse(m.group(1))
+      val time = LocalTime.from(ts)
+      val shiftDate = time match {
+        case t if t.getHour == 23 => LocalDate.from(ts).plusDays(1L)
+        case _ => LocalDate.from(ts)
+      }
+
+      m.group(2) match {
+      case "Guard" => Entry(shiftDate, time, Some(m.group(3).drop(1).toInt), None)
+      case "falls" => Entry(shiftDate, time, None, Some(true))
+      case "wakes" => Entry(shiftDate, time, None, Some(false))
+    }
+  }.get
+}
+
+case class Sleep(id: Int, begin: LocalTime, end: LocalTime)
+
+def buildSleeps(input: List[Entry]): List[Sleep] = {
+  val guardNb = input.filter(_.id.nonEmpty).map(_.id.get).head
+  val sleepCycles = input.filter(e => e.sleep.nonEmpty).map(e => e.time -> e.sleep.get).sortBy(_._1.toSecondOfDay)
+  
+  (sleepCycles.filter(_._2).map(_._1) zip sleepCycles.filterNot(_._2).map(_._1))
+    .map(s => Sleep(guardNb, s._1, s._2))
+}
+
+val entries = Iterator
+  .continually(readLine)
+  .takeWhile(_ != null)
+  .map(parseEntry)
+  .toList
+
+val sleeps = entries.groupBy(_.shiftDate)
+  .flatMap { case (k, v) => buildSleeps(v) }
+
+val sleepers = sleeps
+  .groupBy(_.id).toList
+  .sortBy { case (k, v) => v.map(s => s.end.toSecondOfDay - s.begin.toSecondOfDay).sum }
+  .reverse
+
+val guardId = sleepers.head._1
+
+println(s"Guard ID: $guardId")
+
+val mostAsleepMinute = sleepers.head._2
+  .flatMap(s => s.begin.getMinute.to(s.end.getMinute - 1))
+  .groupBy(identity)
+  .mapValues(_.size)
+  .maxBy(_._2)
+  ._1
+
+println(s"Most asleep minute: $mostAsleepMinute")
+
+println(s"Result: ${guardId * mostAsleepMinute}")