1+ # Given the head of a sorted linked list, delete all nodes that have duplicate
2+ # numbers, leaving only distinct numbers from the original list. Return the
3+ # linked list sorted as well.
4+ 5+ 6+ # Example 1:
7+ # Input: head = [1,2,3,3,4,4,5]
8+ # Output: [1,2,5]
9+ 10+ # Example 2:
11+ # Input: head = [1,1,1,2,3]
12+ # Output: [2,3]
13+ 14+ 15+ # Constraints:
16+ 17+ # The number of nodes in the list is in the range [0, 300].
18+ # -100 <= Node.val <= 100
19+ # The list is guaranteed to be sorted in ascending order.
20+ 21+ 22+ 23+ from typing import Optional
24+ # Definition for singly-linked list.
25+ class ListNode :
26+ def __init__ (self , val = 0 , next = None ):
27+ self .val = val
28+ self .next = next
29+ class Solution :
30+ def deleteDuplicates (self , head : Optional [ListNode ]) -> Optional [ListNode ]:
31+ dummy = ListNode (0 , head )
32+ current = head
33+ prev = dummy
34+ while current :
35+ while current .next and current .val == current .next .val :
36+ current = current .next
37+ if prev .next == current :
38+ prev = prev .next
39+ else :
40+ prev .next = current .next
41+ current = current .next
42+ return dummy .next
43+
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