python: add problem 144 and unittest

Author: supercoderhawk

Python/sln_101_200/solution_141_150.py

@@ -0,0 +1,23 @@
+# -*- coding: utf-8 -*-
+from typing import List
+from common_utils import *
+
+
+class Solution_141_150(object):
+    def preorderTraversal(self, root: TreeNode) -> List[int]:
+        """
+        144
+        :param root:
+        :return:
+        """
+        results = []
+
+        def traversal(node):
+            if not node:
+                return
+            results.append(node.val)
+            traversal(node.left)
+            traversal(node.right)
+
+        traversal(root)
+        return results