Solutions from Scalania 8

build.sbt

@@ -14,7 +14,7 @@ libraryDependencies in Global += "org.specs2" %% "specs2" % "2.4-SNAPSHOT" % "te
 
 resolvers in Global ++= Seq("snapshots", "releases").map(Resolver.sonatypeRepo)
 
-lazy val scalania = project.in(file(".")).aggregate(exercises)
+lazy val scalania = project in file(".") aggregate exercises
 
 lazy val exercises = project
 

exercises/src/main/scala/pl/japila/scalania/package.scala

@@ -0,0 +1,8 @@
+package pl.japila
+
+package object scalania {
+
+  def solutionName(s: Any) =
+    s.getClass.getSimpleName.split("\\$").drop(1).dropRight(1).mkString("_")
+
+}

exercises/src/main/scala/pl/japila/scalania/s99/S99_P20.scala

@@ -1,5 +1,27 @@
 package pl.japila.scalania.s99
 
 object S99_P20 {
-  def removeAt[T](n: Int, ts: Seq[T]): (Seq[T], T) = ???
+
+  val solutions = Seq[(Int, Seq[Any]) => (Seq[Any], Any)](
+    removeAt,
+    removeAt_jacekkolodziejski,
+    removeAt_ajozwik
+  )
+
+  def removeAt[T] = (n: Int, ts: Seq[T]) => ???
+
+  def removeAt_jacekkolodziejski[T] = (n: Int, ts: Seq[T]) =>
+    (ts.take(n) ++ ts.drop(n + 1), ts(n))
+
+  def removeAt_ajozwik[T] = (n: Int, ts: Seq[T]) => {
+    val (l, _, t) = ts.foldLeft[(Seq[T], Int, Option[T])]((Seq[T](), n, None))((acc, el) => {
+      if (acc._2 == 0) {
+        (acc._1, acc._2 - 1, Some(el))
+      } else {
+        (el +: acc._1, acc._2 - 1, acc._3)
+      }
+    }
+    )
+    (l.reverse, t.get)
+  }
 }

exercises/src/main/scala/pl/japila/scalania/s99/S99_P21.scala

@@ -1,5 +1,50 @@
 package pl.japila.scalania.s99
 
 object S99_P21 {
-  def insertAt[T](toAdd: T, position: Int, ts: Seq[T]): Seq[T] = ???
+
+  val solutions = Seq[(Any, Int, Seq[Any]) => Seq[Any]](
+    insertAt,
+    insertAt_tboloo,
+    insertAt_7680700,
+    insertAt_PawelPanasewicz,
+    insertAt_ajozwik
+  )
+
+  def insertAt[T] = (toAdd: T, position: Int, ts: Seq[T]) => ???
+
+  def insertAt_tboloo[T]: (T, Int, Seq[T]) => Seq[T] =
+    (toAdd: T, position: Int, ts: Seq[T]) => {
+      (position, ts) match {
+        case (0, h :: t) => Seq(toAdd) ++ t
+        case (position, h :: t) => Seq(h) ++ insertAt_tboloo(toAdd, position - 1, t)
+      }
+    }
+
+  def insertAt_7680700[T] = (toAdd: T, position: Int, ts: Seq[T]) => {
+    @annotation.tailrec
+    def go(n: Int, l: List[T], r: List[T]): List[T] = {
+      if (n == 0) l.reverse ::: toAdd :: r
+      else go(n - 1, r.head :: l, r.tail)
+    }
+    go(position, Nil, ts.toList)
+  }
+
+  def insertAt_PawelPanasewicz[T] = (toAdd: T, position: Int, ts: Seq[T]) =>
+    ts.patch(position, Seq(toAdd), 0)
+
+  def insertAt_ajozwik[T] = (toAdd: T, position: Int, ts: Seq[T]) => {
+    def insertToAcc: ((Seq[T], Int), T) => (Seq[T], Int) = {
+      (acc, current) =>
+        {
+          val (seq, index) = acc
+          if (index == 0) {
+            (current +: toAdd +: seq, index - 1)
+          } else {
+            (current +: seq, index - 1)
+          }
+        }
+    }
+    val (l, _) = ts.foldLeft[(Seq[T], Int)]((Seq[T](), position))(insertToAcc)
+    l.reverse
+  }
 }

exercises/src/main/scala/pl/japila/scalania/s99/S99_P22.scala

@@ -1,5 +1,48 @@
 package pl.japila.scalania.s99
 
 object S99_P22 {
-  def range(from: Int, to: Int): Seq[Int] = ???
+
+  val solutions = Seq[(Int, Int) => Seq[Int]](
+    range,
+    range_7680926,
+    range_mprowaznik,
+    range_tboloo,
+    range_ajozwik,
+    range_7681054
+  )
+
+  def range = (from: Int, to: Int) => ???
+
+  def range_7680926: (Int, Int) => Seq[Int] = (from, to) => {
+    if (to < from) {
+      throw new IllegalArgumentException("Invalid range")
+    }
+    from match {
+      case `to` => List(from)
+      case x => List(from) ++ range_7680926(from + 1, to)
+    }
+  }
+
+  def range_mprowaznik = (from: Int, to: Int) =>
+    (from to to).toList
+
+  def range_tboloo: (Int, Int) => Seq[Int] = (from, to) =>
+    (from, to) match {
+      case (from, to) if from != to => Seq(from) ++ range_tboloo(from + 1, to)
+      case _ => Nil
+    }
+
+  def range_ajozwik = (from: Int, to: Int) => {
+    def fromN(n: Int): Stream[Int] = n #:: fromN(n + 1)
+    fromN(from).take(to - from + 1).toList
+  }
+
+  def range_7681054 = (from: Int, to: Int) => {
+    @annotation.tailrec
+    def go(i: Int, acc: Seq[Int]): Seq[Int] = {
+      if (i > to) acc.reverse
+      else go(i + 1, i +: acc)
+    }
+    go(from, Seq())
+  }
 }

exercises/src/test/scala/pl/japila/scalania/euler/P01Spec.scala

@@ -1,6 +1,7 @@
 package pl.japila.scalania.euler
 
 import org.specs2.mutable._
+import pl.japila.scalania._
 import Euler_P01._
 
 class P01Spec extends Specification with ExamplesBlock {
@@ -12,6 +13,4 @@ class P01Spec extends Specification with ExamplesBlock {
       }
     }
   }
-
-  def solutionName(s: Any) = s.getClass.getSimpleName.split("\\$").drop(1).dropRight(1).mkString("_")
 }

exercises/src/test/scala/pl/japila/scalania/s99/P20Spec.scala

@@ -1,14 +1,20 @@
 package pl.japila.scalania.s99
 
 import org.specs2.mutable._
-import S99_P20.removeAt
+import pl.japila.scalania._
 
-class P20Spec extends Specification {
+class P20Spec extends Specification with ExamplesBlock {
   "P20 solution" should {
     "Remove the Kth element from a list." in {
-      val (ts, t) = removeAt(1, List('a, 'b, 'c, 'd))
-      ts === List('a, 'c, 'd)
-      t === 'b
+      import S99_P20.solutions
+      solutions.map(s => (s"${solutionName(s)} solution", s)).foreach {
+        case (solution, s) =>
+          solution >> {
+            val (ts, t) = s(1, Seq('a, 'b, 'c, 'd))
+            ts === Seq('a, 'c, 'd)
+            t must_== 'b
+          }
+      }
     }
   }
 }

exercises/src/test/scala/pl/japila/scalania/s99/P21Spec.scala

@@ -1,12 +1,20 @@
 package pl.japila.scalania.s99
 
 import org.specs2.mutable._
-import S99_P21.insertAt
+import pl.japila.scalania._
 
-class P21Spec extends Specification {
+class P21Spec extends Specification with ExamplesBlock {
   "P21 solution" should {
     "Insert an element at a given position into a list." in {
-      insertAt('new, 1, List('a, 'b, 'c, 'd)) === List('a, 'new, 'b, 'c, 'd)
+      import S99_P21.solutions
+      solutions.map(s => (s"${solutionName(s)} solution", s)).foreach {
+        case (solution, s) =>
+          solution >> {
+            val actual = s('new, 1, Seq('a, 'b, 'c, 'd))
+            val expected = Seq('a, 'new, 'b, 'c, 'd)
+            actual === expected
+          }
+      }
     }
   }
 }

exercises/src/test/scala/pl/japila/scalania/s99/P22Spec.scala

@@ -1,12 +1,20 @@
 package pl.japila.scalania.s99
 
 import org.specs2.mutable._
-import S99_P22.range
+import pl.japila.scalania._
 
-class P22Spec extends Specification {
+class P22Spec extends Specification with ExamplesBlock {
   "P22 solution" should {
-    " Create a list containing all integers within a given range." in {
-      range(4, 9) === List(4, 5, 6, 7, 8, 9)
+    "Create a list containing all integers within a given range." in {
+      import S99_P22.solutions
+      solutions.map(s => (s"${solutionName(s)} solution", s)).foreach {
+        case (solution, s) =>
+          solution >> {
+            val actual = s(4, 9)
+            val expected = Seq(4, 5, 6, 7, 8, 9)
+            actual must_== expected
+          }
+      }
     }
   }
 }

exercises/src/test/scala/pl/japila/scalania/s99/P24Spec.scala

@@ -5,7 +5,7 @@ import S99_P24.lotto
 
 class P24Spec extends Specification {
   "P24 solution" should {
-    " Lotto: Draw N different random numbers from the set 1..M." in {
+    "Lotto: Draw N different random numbers from the set 1..M." in {
       val randomrange = lotto(6, 49)
       randomrange.distinct.size === 6
       randomrange.forall(e => 1 <= e && e <= 49) === true

exercises/src/test/scala/pl/japila/scalania/s99/P28Spec.scala

@@ -6,7 +6,7 @@ import S99_P28.lsortFreq
 
 class P28Spec extends Specification {
   "P28a solution" should {
-    " Sort a list of lists according to length of sublists." in {
+    "Sort a list of lists according to length of sublists." in {
       lsort(List(List('a, 'b, 'c), List('d, 'e), List('f, 'g, 'h), List('d, 'e), List('i, 'j, 'k, 'l), List('m, 'n), List('o))) === List(List('o), List('d, 'e), List('d, 'e), List('m, 'n), List('a, 'b, 'c), List('f, 'g, 'h), List('i, 'j, 'k, 'l))
     }
   }