Adding solution-2

W4_2_sum_root_to_leaf.py

@@ -0,0 +1,31 @@
+# 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:
+        self.result = 0
+        self.helper(root, 0)
+        return self.result
+
+    def helper(self, root, curr_sum):
+        #base  
+        if root == None:
+            return
+
+        #logic
+        curr_sum = curr_sum * 10 + root.val
+
+        self.helper(root.left, curr_sum)
+        self.helper(root.right, curr_sum)
+
+        # Check if current node if leaf
+        if root.right == None and root.left == None:
+            self.result = self.result + curr_sum
+
+# Time complexity: O(N), where N is number of nodes in the tree
+# Space compexity: O(H), worst case O(N) - h is the height of the tree
+