Binary Tree Traversal

Inorder Recursive, Inorder Iterative, Preorder Recursive, Preorder Iterative, PostOrder Recursive, PostOrder Iterative, Level-Order Traversals

Author: satyam93sinha

BinaryTreeTraversal.py renamed to Binary Tree Traversal.py

@@ -44,6 +44,26 @@ def inorder_traversal_recur(self, root):
             self.inorder_traversal_recur(root.right)
         else:
             return
+    
+    def inorderTraversalIterative(self, root: TreeNode) -> List[int]:
+        """
+        We need to use a Data Structure which gives us recently visited nodes thus, we use STACK(LIFO). There can be a time when stack
+        is empty but we haven't visited the whole tree/ all the nodes so we iterate until the stack is empty or node!=None.
+        If node is None it means left or right leaf is reached and we need to trace back to recently visited node's parent which isn't
+        yet visited or whose right or left leaves are still unvisited. Keep adding them to the stack and popping them if node is None.
+        """
+        stack = list()
+        inorder_traversal = list()
+        node = root
+        while node or len(stack):
+            if node:
+                stack.append(node)
+                node = node.left
+            else:
+                node = stack.pop()
+                inorder_traversal.append(node.val)
+                node = node.right
+        return inorder_traversal