Remove Nth Node From End of List

Given a linked list, remove the nth node from the end of list and return its head.

For example,

Given linked list: 1->2->3->4->5, and n = 2.

After removing the second node from the end, the linked list becomes 1->2->3->5.

Note:

Given n will always be valid.

Try to do this in one pass.

删除单链表中倒数第n个节点。注意n一直是有效的，所以不用考虑n比链表长度大的情况。还要注意只能遍历一次链表的长度。

/**
* Definition for singly-linked list.
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode removeNthFromEnd(ListNode head, int n) {
if(head==null) return null;
ListNode fakeHead=new ListNode(0);
fakeHead.next=head;
ListNode pre=fakeHead;
ListNode cur=head;
while(cur!=null){
for(int i=0;i<n;i++)
cur=cur.next;
if(cur==null)
return head.next;
while(cur!=null){
cur=cur.next;
pre=pre.next;
}
pre.next=pre.next.next;
}
return fakeHead.next;
}
}