diff -r e7eeeb5b41dc -r 417869f65585 progs/collatz.scala
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/collatz.scala	Sun Nov 06 18:28:47 2016 +0000
@@ -0,0 +1,29 @@
+// Part 1
+
+
+//(1)
+def collatz(n: Long): List[Long] =
+  if (n == 1) List(1) else
+    if (n % 2 == 0) (n::collatz(n / 2)) else 
+      (n::collatz(3 * n + 1))
+
+// an alternative that calculates the steps directly
+def collatz1(n: Long): Int =
+  if (n == 1) 1 else
+    if (n % 2 == 0) (1 + collatz1(n / 2)) else 
+      (1 + collatz1(3 * n + 1))
+
+
+//(2)
+def collatz_max(bnd: Int): Int = {
+  (for (i <- 1 to bnd) yield collatz(i).length).max
+}
+
+
+val bnds = List(10, 100, 1000, 10000, 100000, 1000000, 10000000)
+
+for (bnd <- bnds) {
+  val max = collatz_max(bnd)
+  println(s"In the range of 1 - ${bnd} the maximum steps are ${max}")
+}
+