def remove_duplicate(head):
check = set()
a = head
check.add(a.val)
while a.next:
if a.next.val in check:
basic.remove_node(a)
else:
check.add(a.next.val)
a = a.next
if not a.next:
break
def remove_duplicate_with_sort(head):
z = mergeSort(head)
if not z or not z.next:
return z
first = z
second = z.next
while second:
if first.val == second.val:
basic.remove_node(first)
second = first.next
else:
first = second
second = first.next
return z
