Merge Two Sorted Lists

def mergeTwoLists(list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]: head = cur = ListNode() while list1 and list2: if list1.val <= list2.val: cur.next = ListNode(list1.val) list1 = list1.next else: cur.next = ListNode(list2.val) list2 = list2.next cur = cur.next if list1: cur.next = list1 else: cur.next = list2 return head.next

def mergeTwoLists(self, l1, l2): if l1 is None: return l2 elif l2 is None: return l1 elif l1.val < l2.val: l1.next = self.mergeTwoLists(l1.next, l2) return l1 else: l2.next = self.mergeTwoLists(l1, l2.next) return l2