class Solution:
    def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
        # 1. Create a dummy node to act as the pre-head of the result.
        # This avoids checking if the result head is None during the first iteration.
        dummy = ListNode()
        tail = dummy
        
        # 2. Iterate while both lists have nodes remaining
        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
        
        # 3. Attach the remaining nodes.
        # Since the lists are sorted, we just attach the remainder of the non-empty list.
        # In Python, 'or' returns the first truthy value.
        tail.next = list1 or list2
        
        # 4. Return the next node after dummy (the actual head)
        return dummy.next