LeetCode #21: Merge Two Sorted Lists

LeetCode/easy/merge_two_lists_21.py

@@ -0,0 +1,29 @@
+from typing import Optional
+
+
+class ListNode:
+    def __init__(self, val=0, next=None):
+        self.val = val
+        self.next = next
+
+
+class Solution:
+    def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
+        dummy = ListNode()
+        tail = dummy
+
+        while list1 and list2:
+            if list1.val < list2.val:
+                tail.next = list1
+                list1 = list1.next
+            else:
+                tail.next = list2
+                list2 = list2.next
+            tail = tail.next
+
+        if list1:
+            tail.next = list1
+        else:
+            tail.next = list2
+
+        return dummy.next