#82: Remove Duplicates from Sorted List II

Author: papilo-cloud

Linkedlist/delete_duplicates_II.py

@@ -0,0 +1,43 @@
+# Given the head of a sorted linked list, delete all nodes that have duplicate
+#  numbers, leaving only distinct numbers from the original list. Return the 
+#  linked list sorted as well.
+
+
+# Example 1:
+# Input: head = [1,2,3,3,4,4,5]
+# Output: [1,2,5]
+
+# Example 2:
+# Input: head = [1,1,1,2,3]
+# Output: [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.
+
+
+
+from typing import Optional
+# Definition for singly-linked list.
+class ListNode:
+    def __init__(self, val=0, next=None):
+        self.val = val
+        self.next = next
+class Solution:
+    def deleteDuplicates(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        dummy = ListNode(0, head)
+        current = head
+        prev = dummy
+        while current:
+            while current.next and current.val == current.next.val:
+                current = current.next
+            if prev.next == current:
+                prev = prev.next
+            else:
+                prev.next = current.next
+            current = current.next
+        return dummy.next
+