1721

1721. Swapping Nodes in a Linked List

The solution is as follows:

class Solution:
    def deleteDuplicates(self, head: Optional[ListNode]) -> Optional[ListNode]:
        dummy = curr = ListNode(-1, head)
 
        while curr:
            if curr.next and curr.next.next and curr.next.val == curr.next.next.val:
                dup = curr.next.val
 
                while curr.next and curr.next.val == dup:
                    curr.next = curr.next.next
            else:
                curr = curr.next
 
        return dummy.next

_ Time Complexity:

O(n) - We traverse all nodes within the linked list.

_ Space Complexity:

O(1) - We maintain pointers that occupy constant space.