def merge_two_lists(self, l1, l2):
node = ListNode(-1)
start = node
while l1 is not None and l2 is not None:
if l1.val <= l2.val:
node.next = l1
l1 = l1.next
else:
node.next = l2
l2 = l2.next
node = node.next
if l1 is not None:
node.next = l1
if l2 is not None:
node.next = l2
return start.next
def parse_line(line):
groups = re.search(r'(\d+) <-> ([\d,\s]+)', line).groups()
node = Node(groups[0])
node.next = set(groups[1].replace(' ', '').split(','))
return node
