add some fun tree playing

trees_and_graphs/preorder_transversal.py

@@ -0,0 +1,28 @@
+# recursive and iterative inorder traversal
+
+def preorder_recursive(root: Optional[TreeNode]) -> list[int]:
+       
+        if root == None:
+                return []
+        
+        return [root.val] + preorder_recursive(root.left) + preorder_recursive(root.right)
+    
+
+def preorder_iterative(root: Optional[TreeNode]) -> list[int]:
+        
+        result = []
+        stack = [root]
+        
+        while stack:
+            
+            current = stack.pop()
+            result.append(current.val)
+            
+            if current.right:
+                stack.append(current.right)
+                
+            if current.left:
+                stack.append(current.left)
+            
+        return result
+