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Cheryl's birthday: Difference between revisions
Scala contribution added.
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=={{header|Scala}}==
==={{trans|D}}===
<lang scala>import java.time.format.DateTimeFormatter
import java.time.{LocalDate, Month}
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{{out}}
<pre>July 16</pre>
===Scala-ish approach===
{{Out}}See it yourself by running in your browser either by [https://scalafiddle.io/sf/AiS6u7B/0 ScalaFiddle (ES aka JavaScript, non JVM)] or [https://scastie.scala-lang.org/hoBvwq5fSkSRk0vnr6NKmA Scastie (remote JVM)].
{{libheader|Scala Math Puzzle}}
{{libheader|Scala Scala-ish }}
{{libheader|Scala Type parameters}}
{{libheader|ScalaFiddle qualified}}
{{libheader|Scastie qualified}}
{{works with|Scala|2.13}}
<lang Scala>object Cheryl_sBirthday extends App {
private val possiblerDates = Set(
Date("May", 15), Date("May", 16), Date("May", 19),
Date("June", 17), Date("June", 18),
Date("July", 14), Date("July", 16),
Date("August", 14), Date("August", 15), Date("August", 17)
)
private def clou3: Date = {
// Find the dates with ONE unique once and only occurrence of the day of the month.
def onceDates[K](toBeExcluded: Set[Date], selector: Date => K): Seq[Date] =
toBeExcluded.groupBy(selector).filter { case (_, multiSet) => multiSet.size == 1 }.values.flatten.toSeq
// 1) Albert tells us that Bernard doesn't know the answer,
// so we know the answer must be in months that does NOT have a same day of month.
val uniqueMonths = onceDates(possiblerDates, (date: Date) => date.dayOfMonth).map(_.month)
// Remove the dates with those months. The dates remain which has NOT those months.
val clou1 = possiblerDates.filterNot(p => uniqueMonths.contains(p.month))
// 2) Since Bernard now knows the answer, that tells us that the day MUST be unique among the remaining birthdays.
val uniqueDays = onceDates(clou1, (date: Date) => date.dayOfMonth).map(_.dayOfMonth)
// 3) Since Albert now knows the answer, that tells us the answer has to be unique by month.
// First, as the first parameter, intersect clou1 (Albert) with uniqueDays (Bernard)
onceDates(clou1.filter(date => uniqueDays.contains(date.dayOfMonth)), (date: Date) => date.month).head
}
case class Date(month: String, dayOfMonth: Int) {
override def toString: String = s"${"🎂 " * 3}$dayOfMonth $month${" 🎂" * 3}"
}
println(clou3)
}</lang>
=={{header|Sidef}}==
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