Create 0144-binary-tree-preorder-traversal.py

Author: neetcode-gh

Diff for: python/0144-binary-tree-preorder-traversal.py

@@ -0,0 +1,12 @@
+class Solution:
+    def preorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
+        cur, stack = root, []
+        res = []
+        while cur or stack:
+            if cur:
+                res.append(cur.val)
+                stack.append(cur.right)
+                cur = cur.left
+            else:
+                cur = stack.pop()
+        return res