--- a/testing1/collatz.scala	Tue Nov 12 10:47:27 2019 +0000
+++ b/testing1/collatz.scala	Tue Nov 19 00:40:27 2019 +0000
@@ -1,51 +1,70 @@
-// Part 1 about the 3n+1 conjecture
-//==================================
+object CW6a {
 
-// generate jar with
-//   > scala -d collatz.jar  collatz.scala
-
-object CW6a { 
+//(1) Complete the collatz function below. It should
+//    recursively calculate the number of steps needed 
+//    until the collatz series reaches the number 1.
+//    If needed, you can use an auxiliary function that
+//    performs the recursion. The function should expect
+//    arguments in the range of 1 to 1 Million.
 
 
-/*
- * def collatz(n: Long): Long =
-  if (n == 1) 0 else
-    if (n % 2 == 0) 1 + collatz(n / 2) else 
-      1 + collatz(3 * n + 1)
-*/
+// def collatz(n: Long) : Long = {
+//     if (n == 1) 1 //else
+//     // if (n % 2 == 0) {
+//     //     collatz(n/2)
+//     //     steps + 1
+//     // } //else
+//     // if (n % 2 != 0) {
+//     //     collatz((3 * n) + 1)
+//     //     steps + 1
+//     // }
+// }
+
+// val steps: Long = 1
+// val lst = List()
+// def collatz(n: Long) : Long = {
+//     if  (n == 1) { steps + 1 }
+//     else if (n % 2 == 0) { 
+//         collatz(n/2);
+//     }
+//     else { 
+//         collatz((3 * n) + 1);
+//     }
+//     steps + 1
+// } 
+// collatz(6)
 
-def collatz_max(bnd: Long): (Long, Long) = {
-  val all = for (i <- (1L to bnd)) yield (collatz(i), i)
-  all.maxBy(_._1)
+def collatz(n: Long, list: List[Long] = List()): Long = {
+    if (n == 1) {
+            n :: list
+            list.size.toLong
+    }
+    else if (n % 2 == 0) {
+        collatz(n / 2, n :: list)
+    }
+    else {
+        collatz((3 * n) + 1, n :: list)
+    }
+}   
+
+val test = collatz(6)
+
+//(2) Complete the collatz_max function below. It should
+//    calculate how many steps are needed for each number 
+//    from 1 up to a bound and then calculate the maximum number of
+//    steps and the corresponding number that needs that many 
+//    steps. Again, you should expect bounds in the range of 1
+//    up to 1 Million. The first component of the pair is
+//    the maximum number of steps and the second is the 
+//    corresponding number.
+
+//def collatz_max(bnd: Long) : (Long, Long) = ...
+def collatz_max(bnd: Long) : (Long, Long) = {
+    val stepsTable = for (n <- (1 to bnd.toInt).toList) yield (collatz(n), n.toLong)
+    //println(stepsTable)
+    stepsTable.max
 }
 
 
-/* some test cases
-val bnds = List(10, 100, 1000, 10000, 100000, 1000000)
-
-for (bnd <- bnds) {
-  val (steps, max) = collatz_max(bnd)
-  println(s"In the range of 1 - ${bnd} the number ${max} needs the maximum steps of ${steps}")
 }
 
-*/
-
-
-
-
-def collatz(n: Long) : Long = {
-    if (n == 1) {
-        1L
-    } else {
-        if (n % 2 == 0) {
-            collatz(n/2) + 1
-        } else {
-            collatz((n*3)+1) + 1
-        }
-    }
-}
-
-}
-
-
-