Data commit

Task/Five-weekends/Scala/five-weekends.scala

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+import java.util.Calendar._
+import java.util.GregorianCalendar
+
+import org.scalatest.{FlatSpec, Matchers}
+
+class FiveWeekends extends FlatSpec with Matchers {
+
+  case class YearMonth[T](year: T, month: T)
+  implicit class CartesianProd[T](val seq: Seq[T]) {
+    def x(other: Seq[T]) = for(s1 <- seq; s2 <- other) yield YearMonth(year=s1,month=s2)
+    def -(other: Seq[T]): Seq[T] = seq diff other
+  }
+
+  def has5weekends(ym: { val year: Int; val month: Int}) = {
+    val date = new GregorianCalendar(ym.year, ym.month-1, 1)
+    date.get(DAY_OF_WEEK) == FRIDAY && date.getActualMaximum(DAY_OF_MONTH) == 31
+  }
+
+  val expectedFirstFive = Seq(
+    YearMonth(1901,3), YearMonth(1902,8), YearMonth(1903,5), YearMonth(1904,1), YearMonth(1904,7))
+  val expectedFinalFive = Seq(
+    YearMonth(2097,3), YearMonth(2098,8), YearMonth(2099,5), YearMonth(2100,1), YearMonth(2100,10))
+  val expectedNon5erYears = Seq(1900, 1906, 1917, 1923, 1928, 1934, 1945, 1951, 1956, 1962,
+                                1973, 1979, 1984, 1990, 2001, 2007, 2012, 2018, 2029, 2035,
+                                2040, 2046, 2057, 2063, 2068, 2074, 2085, 2091, 2096)
+
+  "Five Weekend Algorithm" should "match specification" in {
+    val months = (1900 to 2100) x (1 to 12) filter has5weekends
+    months.size shouldBe 201
+    months.take(5) shouldBe expectedFirstFive
+    months.takeRight(5) shouldBe expectedFinalFive
+
+    (1900 to 2100) - months.map(_.year) shouldBe expectedNon5erYears
+  }
+}