recursive solution

297. Serialize and Deserialize Binary Tree.py

@@ -5,8 +5,6 @@
 #         self.left = None
 #         self.right = None
 
-from queue import Queue
-
 
 class Codec:
     def serialize(self, root):
@@ -16,65 +14,25 @@ def serialize(self, root):
         :rtype: str
         """
         if not root:
-            return ''
-        lst = []
-        q = Queue()
-        q.put(root)
-        while not q.empty():
-            node = q.get()
-            if not node:
-                lst.append(None)
-                continue
-            lst.append(node.val)
-            q.put(node.left)
-            q.put(node.right)
-        return ','.join(str(x) for x in lst)
+            return '# '
+        return str(root.val) + ' ' + self.serialize(root.left) + self.serialize(root.right)
 
     def deserialize(self, data):
         """Decodes your encoded data to tree.
         
         :type data: str
         :rtype: TreeNode
         """
-        if not data:
-            return None
-        lst = [
-            int(x) if x.lstrip('-').isdigit() else None
-            for x in data.split(',')
-        ]
-        q = Queue()
-        root = TreeNode(lst[0])
-        q.put(root)
-        length = len(lst)
-        idx = 0
-        while not q.empty():
-            node = q.get()
-            idx += 1
-            if idx == length:
-                break
-            if lst[idx] is not None:
-                left = TreeNode(lst[idx])
-                node.left = left
-                q.put(left)
-            idx += 1
-            if idx == length: break
-            if lst[idx] is not None:
-                right = TreeNode(lst[idx])
-                node.right = right
-                q.put(right)
-
-        return root
-
-        # def construct(lst, idx):
-        #     if lst[idx] is None:
-        #         return None
-        #     node = TreeNode(lst[idx])
-        #     left = idx * 2 + 1
-        #     right = idx * 2 + 2
-        #     if left < len(lst):
-        #         node.left = construct(lst, left)
-        #         node.right = construct(lst, right)
-        #     return node
+        def des():
+            val = next(it)
+            if val == '#':
+                return None
+            node = TreeNode(int(val))
+            node.left = des()
+            node.right = des()
+            return node
+        it = iter(data.split())
+        return des()
 
 
 # Your Codec object will be instantiated and called as such: