82. 刪除排序連結串列中的重複元素 II

Difficulty: 中等

給定一個排序連結串列，刪除所有含有重複數字的節點，只保留原始連結串列中_沒有重複出現_的數字。

示例1:

輸入: 1->2->3->3->4->4->5
輸出: 1->2->5

示例2:

輸入: 1->1->1->2->3
輸出: 2->3

Solution

# Definition for singly-linked list.
# class ListNode:
#   def __init__(self, x):
#     self.val = x
#     self.next = None
​
class Solution:
  def deleteDuplicates(self, head: ListNode) -> ListNode:
    if not head: return None
    res = ListNode(-1)
    res.next = head
    pre = res
    
    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 res.next