added binary tree traversals

Author: sloloris

chapter-4-trees-and-graphs/binary-tree-traversal.py

@@ -0,0 +1,25 @@
+# In-Order Traversal - visit (here, print) the (1) left branch, (2) current node, (3) right branch. This visits the nodes of a BST in ascending order.
+
+def in_order_traversal(node):
+    if node:
+        in_order_traversal(node.left)
+        print node.data
+        in_order_traversal(node.right)
+
+
+# Pre-Order Traversal - visit the (1) current node, (2) child nodes (probably left to right)
+
+def pre_order_traversal(node):
+    if node:
+        print node.data
+        pre_order_traversal(node.left)
+        pre_order_traversal(node.right)
+
+
+# Post-Order Traversal - visit the current node after its child nodes. The root is always the last node visited
+
+def post_order_traversal(node):
+    if node:
+        post_order_traversal(node.left)
+        post_order_traversal(node.right)
+        print node.data