June 2018 Update

Task/Look-and-say-sequence/Scala/look-and-say-sequence-1.scala

@@ -1,11 +1,27 @@
-def lookAndSay(seed: BigInt) = {
-  val s = seed.toString
-  ( 1 until s.size).foldLeft((1, s(0), new StringBuilder)) {
-    case ((len, c, sb), index) if c != s(index) => sb.append(len); sb.append(c); (1, s(index), sb)
-    case ((len, c, sb), _) => (len + 1, c, sb)
-  } match {
-    case (len, c, sb) => sb.append(len); sb.append(c); BigInt(sb.toString)
-  }
-}
+import scala.annotation.tailrec
 
-def lookAndSayIterator(seed: BigInt) = Iterator.iterate(seed)(lookAndSay)
+object LookAndSay extends App {
+
+  loop(10, "1")
+
+  @tailrec
+  private def loop(n: Int, num: String): Unit = {
+    println(num)
+    if (n <= 0) () else loop(n - 1, lookandsay(num))
+  }
+
+  private def lookandsay(number: String): String = {
+    val result = new StringBuilder
+
+    @tailrec
+    def loop(numberString: String, repeat: Char, times: Int): String =
+      if (numberString.isEmpty) result.toString()
+      else if (numberString.head != repeat) {
+        result.append(times).append(repeat)
+        loop(numberString.tail, numberString.head, 1)
+      } else loop(numberString.tail, numberString.head, times + 1)
+
+    loop(number.tail + " ", number.head, 1)
+  }
+
+}

Task/Look-and-say-sequence/Scala/look-and-say-sequence-2.scala

@@ -1,17 +1,11 @@
-object Main extends App {
-
-  def lookAndSay(previous: List[BigInt]): Stream[List[BigInt]] = {
-
-    def next(num: List[BigInt]): List[BigInt] = num match {
-      case Nil => Nil
-      case head :: Nil => 1 :: head :: Nil
-      case head :: tail =>
-        val size = (num takeWhile (_ == head)).size
-        List(BigInt(size), head) ::: next(num.drop(size))
-    }
-    val x = next(previous)
-    x #:: lookAndSay(x)
+def lookAndSay(seed: BigInt) = {
+  val s = seed.toString
+  ( 1 until s.size).foldLeft((1, s(0), new StringBuilder)) {
+    case ((len, c, sb), index) if c != s(index) => sb.append(len); sb.append(c); (1, s(index), sb)
+    case ((len, c, sb), _) => (len + 1, c, sb)
+  } match {
+    case (len, c, sb) => sb.append(len); sb.append(c); BigInt(sb.toString)
   }
-
-  (lookAndSay(1 :: Nil) take 10).foreach(s => println(s.mkString("")))
 }
+
+def lookAndSayIterator(seed: BigInt) = Iterator.iterate(seed)(lookAndSay)

Task/Look-and-say-sequence/Scala/look-and-say-sequence-3.scala

@@ -0,0 +1,17 @@
+object Main extends App {
+
+  def lookAndSay(previous: List[BigInt]): Stream[List[BigInt]] = {
+
+    def next(num: List[BigInt]): List[BigInt] = num match {
+      case Nil => Nil
+      case head :: Nil => 1 :: head :: Nil
+      case head :: tail =>
+        val size = (num takeWhile (_ == head)).size
+        List(BigInt(size), head) ::: next(num.drop(size))
+    }
+    val x = next(previous)
+    x #:: lookAndSay(x)
+  }
+
+  (lookAndSay(1 :: Nil) take 10).foreach(s => println(s.mkString("")))
+}