--- a/pre_testing1/collatz.scala	Tue Nov 17 00:34:55 2020 +0000
+++ b/pre_testing1/collatz.scala	Wed Nov 18 01:54:39 2020 +0000
@@ -1,54 +1,59 @@
-object CW6a {
+// Basic Part about the 3n+1 conjecture
+//==================================
+
+// generate jar with
+//   > scala -d collatz.jar  collatz.scala
+
+object CW6a { // for purposes of generating a jar
 
-//(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) 1 + collatz( n / 2);
-    else 1 + collatz( n * 3 + 1);
+def aux(n: Long, acc: Long) : Long =
+  if (n == 1) acc else
+    if (n % 2 == 0) aux(n / 2, acc + 1) else
+      aux(3 * n + 1, acc + 1)
 
 
-//(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(n: Long): Long = aux(n, 0)
+
+def collatz_max(bnd: Long): (Long, Long) = {
+  val all = for (i <- (1L to bnd)) yield (collatz(i), i)
+  all.maxBy(_._1)
+}
 
-def collatz_max(bnd: Long) : (Long, Long) =
-     ((1.toLong to bnd).toList.map
-        (n => collatz(n)).max ,
-            (1.toLong to bnd).toList.map
-                (n => collatz(n)).indexOf((1.toLong to bnd).toList.map
-                    (n => collatz(n)).max) + 1);
+//collatz_max(1000000)
+//collatz_max(10000000)
+//collatz_max(100000000)
+
+/* some test cases
+val bnds = List(10, 100, 1000, 10000, 100000, 1000000)
 
-//(3) Implement a function that calculates the last_odd
-//    number in a collatz series.  For this implement an
-//    is_pow_of_two function which tests whether a number
-//    is a power of two. The function is_hard calculates
-//    whether 3n + 1 is a power of two. Again you can
-//    assume the input ranges between 1 and 1 Million,
-//    and also assume that the input of last_odd will not
-//    be a power of 2.
-//idk
- def is_pow_of_two(n: Long) : Boolean =
-    if ( n & ( n - 1) == 0) true;
-    else false;
+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 is_hard(n: Long) : Boolean =
-    if ( (3*n + 1) & 3*n == 0) true;
-    else false;
+def is_pow(n: Long) : Boolean = (n & (n - 1)) == 0
+
+def is_hard(n: Long) : Boolean = is_pow(3 * n + 1)
+
+def last_odd(n: Long) : Long = 
+  if (is_hard(n)) n else
+    if (n % 2 == 0) last_odd(n / 2) else 
+      last_odd(3 * n + 1)
 
 
-def last_odd(n: Long) : Long = ???
+//for (i <- 130 to 10000) println(s"$i: ${last_odd(i)}")
+//for (i <- 1 to 100) println(s"$i: ${collatz(i)}")
+
+}
 
 
 
-}