--- a/progs/lecture2.scala	Fri Apr 10 12:12:48 2020 +0100
+++ b/progs/lecture2.scala	Thu Apr 23 14:49:54 2020 +0100
@@ -655,3 +655,24 @@
 
 
 
+
+
+
+/*
+ *               1
+  *             / |  \
+  *           /   |   \
+  *         /     |    \
+  *        2      3     8
+  *      /  \    / \   / \
+  *     4    5  6   7 9  10
+  * Preorder: 1,2,4,5,3,6,7,8,9,10
+  * InOrder: 4,2,5,1,6,3,7,9,8,10
+  * PostOrder: 4,5,2,6,7,3,9,10,8,1
+  *
+ 
+show inorder, preorder, postorder
+
+
+
+*/