diff --git a/maximum-depth-of-binary-tree/doh6077.py b/maximum-depth-of-binary-tree/doh6077.py
new file mode 100644
index 0000000000..3b05278afd
--- /dev/null
+++ b/maximum-depth-of-binary-tree/doh6077.py
@@ -0,0 +1,11 @@
+
+# Time: O(n)
+# Maximum Depth of Binary Tree 
+class Solution:
+    def maxDepth(self, root: Optional[TreeNode]) -> int:
+        if not root:
+            return 0 # base case 
+        left = self.maxDepth(root.left)
+        right = self.maxDepth(root.right)
+
+        return 1 + max(left, right)
diff --git a/merge-two-sorted-lists/doh6077.py b/merge-two-sorted-lists/doh6077.py
new file mode 100644
index 0000000000..ba96bc5db4
--- /dev/null
+++ b/merge-two-sorted-lists/doh6077.py
@@ -0,0 +1,17 @@
+
+# 21. Merge Two Sorted Lists
+
+class Solution:
+    def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
+        tempNode = ListNode() 
+        node = tempNode
+        while list1 and list2:
+            if list1.val < list2.val:
+                node.next = list1
+                list1 = list1.next
+            else:
+                node.next = list2
+                list2 = list2.next
+            node = node.next 
+        node.next = list1 or list2
+        return tempNode.next