Given the head
of a sorted linked list, delete all duplicates such that each element appears only once. Return the linked list sorted as well.
Example 1:
1 > 1 > 2

v
1 > 2
Input: head = [1,1,2]
Output: [1,2]
Example 2:
1 > 1 > 2 > 3 > 3

v
1 > 2 > 3
Input: head = [1,1,2,3,3]
Output: [1,2,3]
Constraints:
 The number of nodes in the list is in the range
[0, 300]
.
 100 <=
Node.val
<= 100
 The list is guaranteed to be sorted in ascending order.
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# Definition for singlylinked list.
# class ListNode:
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next
''' Recursive '''
class Solution:
def deleteDuplicates(self, head: Optional[ListNode]) > Optional[ListNode]:
if not head or not head.next:
return head
head.next = self.deleteDuplicates(head.next)
if head.val == head.next.val:
return head.next
return head
''' Iterative '''
class Solution:
def deleteDuplicates(self, head: Optional[ListNode]) > Optional[ListNode]:
current = head
while current and current.next:
if current.next.val == current.val:
current.next = current.next.next
else:
current = current.next
return head
