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Remove Duplicates from Sorted List II

Problem Statement​

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. Leetcode Link

Example 1:​

Image of Yaktocat

Input: head = [1,2,3,3,4,4,5]

Output: [1,2,5]

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.

Code​

Python Code
class Solution:
    def deleteDuplicates(self, head):
        dummy = pre = ListNode(0)
        dummy.next = head
        while head and head.next:
            if head.val == head.next.val:
                while head and head.next and head.val == head.next.val:
                    head = head.next
                head = head.next
                pre.next = head
            else:
                pre = pre.next
                head = head.next
        return dummy.next