Added 4 questions

Python/101.SymetricTree.py

@@ -0,0 +1,9 @@
+class Solution:
+    def isSymmetric(self, root: Optional[TreeNode]) -> bool:
+        def isMirror(left, right):
+            if left == None and right == None:
+                return True
+            if left == None or right == None:
+                return False
+            return (left.val == right.val) and isMirror(left.right, right.left) and isMirror(left.left, right.right)
+        return isMirror(root, root)

Python/104.MaximumDepthofBinaryTree.py

@@ -0,0 +1,13 @@
+# 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 maxDepth(self, root: Optional[TreeNode]) -> int:
+        if root == None:
+            return 0
+        else:
+            return max(self.maxDepth(root.left), self.maxDepth(root.right)) + 1
+

Python/108.ConvertSortedArraytoBinarySearchTree.py

@@ -0,0 +1,15 @@
+# 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 sortedArrayToBST(self, nums: List[int]) -> Optional[TreeNode]:
+        if len(nums) == 0:
+            return None
+        if len(nums) == 1:
+            return TreeNode(nums[0])
+        mid = len(nums) // 2
+        return TreeNode(nums[mid], self.sortedArrayToBST(nums[:mid]), self.sortedArrayToBST(nums[mid+1:]))
+

Python/129.SumRootToLeafNumber.py

@@ -0,0 +1,16 @@
+# 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: Optional[TreeNode]) -> int:
+        def dfs(node, current):
+            if node == None:
+                return 0
+            current = current * 10 + node.val
+            if node.left == None and node.right == None:
+                return current
+            return dfs(node.left, current) + dfs(node.right, current)
+        return dfs(root, 0)