Leetcode 83. Remove Duplicates from Sorted List

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

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

 

思路和在sorted array中去重差不多。注意L22如果不comment掉会出错。原因是，while head.next 要求list的长度至少为2。如果初始的list 是 1 -> 1 -> None。如果执行L22，那么head = None，while head.next 会出错。

# 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
        
        dummy = head
        while head.next:
            if head.next.val != head.val:
                head = head.next
            else:
                head.next = head.next.next
        #        head = head.next
        return dummy