[leetcode] @python 82. Remove Duplicates from Sorted List II

题目链接

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

题目原文

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.

题目大意

清除链表中的有重复元素

解题思路

用两个指针pre cur
1.ans.next= head 2.pre=anscur=ans,next 3.当指针移到 pre.next 和cur.next 不等的位置,将这个位置加入到 pre.next中去 4.否者就跳过cur

代码

# 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(0)
        ans.next = head
        
        pre = ans
        cur = ans.next
        
        while cur != None:
            while cur.next and cur.next.val == pre.next.val:
                cur = cur.next
            if pre.next == cur:
                pre = pre.next
            else:
                pre.next = cur.next
            cur = cur.next
        return ans.next