【leetcode】Remove Duplicates from Sorted List

題目簡述

Given a sorted linked list, delete all duplicates such that each element appear only once.

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

解題思路

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

class Solution:
    # @param head, a ListNode
    # @return a ListNode
    def deleteDuplicates(self, head):
        if head == None:
            return head
        pre = ListNode(-1)
        p = ListNode(-1)
        p = pre = head
        while p != None:
            if p.val == pre.val:
                if p.next == None:
                    pre.next = None
                else:
                    pre.next = p.next
                p = pre.next
            else:
                p = p.next
                pre = pre.next
        return head