diff --git a/leetcode_106.py b/leetcode_106.py
new file mode 100644
index 00000000..5ebdcec7
--- /dev/null
+++ b/leetcode_106.py
@@ -0,0 +1,20 @@
+class Solution:
+    def buildTree(self, inorder: List[int], postorder: List[int]) -> Optional[TreeNode]:
+        idx = {val: i for i, val in enumerate(inorder)}
+        self.post_idx = len(postorder) - 1
+
+        def helper(left, right):
+            if left > right:
+                return None
+
+            root_val = postorder[self.post_idx]
+            self.post_idx -= 1
+            root = TreeNode(root_val)
+
+            mid = idx[root_val]
+
+            # build right subtree first
+            root.right = helper(mid + 1, right)
+            root.left = helper(left, mid - 1)
+
+            return root
\ No newline at end of file
diff --git a/leetcode_129.py b/leetcode_129.py
new file mode 100644
index 00000000..54497c31
--- /dev/null
+++ b/leetcode_129.py
@@ -0,0 +1,14 @@
+class Solution:
+    def sumNumbers(self, root: Optional[TreeNode]) -> int:
+        def dfs(node, curr):
+            if not node:
+                return 0
+
+            curr = curr * 10 + node.val
+
+            if not node.left and not node.right:
+                return curr
+
+            return dfs(node.left, curr) + dfs(node.right, curr)
+
+        return dfs(root, 0)
\ No newline at end of file