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82. Remove Duplicates from Sorted List II

Difficulty Topics

Description

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.

Solution

remove-duplicates-from-sorted-list-ii.py
# 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]:
        curr = res = ListNode(-1, head)

        while curr:
            if curr.next and curr.next.next and curr.next.val == curr.next.next.val:
                v = curr.next.val
                p = curr.next

                while p and p.val == v:
                    p = p.next

                curr.next = p
            else:
                curr = curr.next

        return res.next