leetcode-----Remove Linked List Elements

标题：	Remove Linked List Elements
通过率：	30.5%
难度：	简单

Remove all elements from a linked list of integers that have value val.

Example
Given: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6
Return: 1 --> 2 --> 3 --> 4 --> 5

Credits:
Special thanks to @mithmatt for adding this problem and creating all test cases.

本题就是一个很普通的链表节点删除，需要注意的是开始时在原有的链表的头结点前加一个无关的头，代码如下：

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

class Solution:
    # @param {ListNode} head
    # @param {integer} val
    # @return {ListNode}
    def removeElements(self, head, val):
        if head==None:return head
        pre=ListNode(-1)
        pre.next=head
        res,first,second=pre,pre,head
        while second!= None:
            if second.val==val:
                first.next=second.next
                second=second.next
            else:first,second=second,second.next
        return pre.next