working solution

problem1.py

@@ -0,0 +1,29 @@
+# problem 1 
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def buildTree(self, inorder: List[int], postorder: List[int]) -> Optional[TreeNode]:
+        if len(postorder) == 0:
+            return None
+        root_val = postorder[-1]
+        root_val_idx = -1
+        for i in range(len(inorder)):
+            if inorder[i] == root_val:
+                root_val_idx = i
+                break
+
+        left_inorder = inorder[0:root_val_idx]
+        right_inorder = inorder[root_val_idx+1:]
+
+        left_postorder = postorder[0:len(left_inorder)]
+        right_postorder = postorder[len(left_inorder):-1]
+
+        node = TreeNode(root_val)
+        node.left = self.buildTree(left_inorder,left_postorder)
+        node.right = self.buildTree(right_inorder,right_postorder)
+
+        return node

problem2.py

@@ -0,0 +1,23 @@
+# problem 2 
+
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+
+    def helper(self,root_node,count):
+        if root_node is None:
+            return 
+        count = (count * 10) + root_node.val
+        if root_node.left is None and root_node.right is None:
+            self.count+=count
+        self.helper(root_node.left,count)
+        self.helper(root_node.right,count)
+
+    def sumNumbers(self, root: Optional[TreeNode]) -> int:
+        self.count = 0 
+        self.helper(root,0)
+        return self.count