[LeetCode] 83. Remove Duplicates from Sorted List_Easy tag: Linked List

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

Example 1:

Input: 1->1->2
Output: 1->2

Example 2:

Input: 1->1->2->3->3
Output: 1->2->3


COde

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def deleteDuplicates(self, head: ListNode) -> ListNode:
        dummy = head
        while head and head.next:
            if head.val == head.next.val:
                head.next = head.next.next
            else:
                head = head.next
        return dummy

 

利用dummy来记住head，pre去记录上一个node，将head 和pre 比较（如果pre存在的话）， 一旦相等，则删除掉head该点。注意，那个点实际上还是在，但是根据python的回收机制，没有指针指向该点，会被回收掉。
(也可以像code中那样，将head.next = None)

Code

class ListNode:
    def __init__(self, x):
        self.val = x
        self.next = None

class Solution:
    def removeDup(self, head):
        dummy, pre = head, None
        while head:
            if pre and head.val == pre.val:
                pre.next = head.next
                head.next = None
            else:
　　　　　　　　   pre = head
            head = pre.next
        return dummy