[LeetCode]题解（python）：082

题目来源

https://leetcode.com/problems/remove-duplicates-from-sorted-list-ii/

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

For example,
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

题意分析

Input:

:type head: ListNode

Output:

:rtype: ListNode

Conditions:与83题不同，只要元素出现过，则将该元素去掉

题目思路

因为list是有序的，并且可能返回一个空list，所以增加一个头节点。再增加一个节点时，就看这个节点之后是否有值与这个节点的值重复，如果有就不加这个值的【所有】节点

AC代码（Python）

 1 # Definition for singly-linked list.
 2 # class ListNode(object):
 3 #     def __init__(self, x):
 4 #         self.val = x
 5 #         self.next = None
 6 
 7 class Solution(object):
 8     def deleteDuplicates(self, head):
 9         """
10         :type head: ListNode
11         :rtype: ListNode
12         """
13         if head == None or head.next == None:
14             return head
15         
16         ans = ListNode(-1)
17         ans.next = head
18         p = ans
19         temp = p.next
20         
21         while p.next:
22             while temp.next and temp.next.val == p.next.val:
23                 temp = temp.next
24             if p.next == temp:
25                 p = p.next
26                 temp = p.next
27             else:
28                 p.next = temp.next
29         
30         return ans.next
31             
32