[LeetCode]题解（python）：082

题目来源

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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.

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题意分析

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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

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题目思路

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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

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AC代码（Python）

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def deleteDuplicates(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        if head == None or head.next == None:
            return head
        
        ans = ListNode(-1)
        ans.next = head
        p = ans
        temp = p.next
        
        while p.next:
            while temp.next and temp.next.val == p.next.val:
                temp = temp.next
            if p.next == temp:
                p = p.next
                temp = p.next
            else:
                p.next = temp.next
        
        return ans.next