leetcode 【 Remove Duplicates from Sorted List 】 python 实现

题目：

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.

代码：

# 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 is None or head.next is None:
            return head
        
        dummyhead = ListNode(0)
        dummyhead.next = head
        p = dummyhead.next
        
        while p.next is not None:
            if p.val == p.next.val:
                p.next = p.next.next
            else:
                p = p.next
        
        return dummyhead.next

思路：

设立虚表头dummyhead

遇上val不同的，再执行 p=p.next；否则指针p不动，只是p.next变化。