Completed trees-2

Problem_1.py

@@ -0,0 +1,25 @@
+# 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, postorder):
+        n = len(inorder)
+        self.index = n - 1
+        self.in_map = {}
+        for i in range(n):
+            ele = inorder[i]
+            self.in_map[ele] = i
+        return self.helper(postorder, 0, n - 1)
+
+    def helper(self, postorder, start, end):
+        if start > end:
+            return None
+        root = TreeNode(postorder[self.index])
+        idx = self.in_map[root.val]
+        self.index -= 1
+        root.right = self.helper(postorder, idx + 1, end)
+        root.left = self.helper(postorder, start, idx - 1)
+        return root

Problem_2.py

@@ -0,0 +1,17 @@
+# 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 sumNumbers(self, root):
+        return self.helper(root, 0)
+
+    def helper(self, root, prevSum):
+        if not root:
+            return 0
+        prevSum = prevSum * 10 + root.val
+        if not root.left and not root.right:
+            return prevSum
+        return self.helper(root.left, prevSum) + self.helper(root.right, prevSum)