题目：删除链表中倒数第n个节点

给定一个链表，删除链表中倒数第n个节点，返回链表的头节点。

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样例

给出链表1->2->3->4->5->null和 n = 2.

删除倒数第二个节点之后，这个链表将变成1->2->3->5->null.

注意

链表中的节点个数大于等于n

挑战

O(n)时间复杂度

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/**

* Definition for ListNode.

* public class ListNode {

* int val;

* ListNode next;

* ListNode(int val) {

* this.val = val;

* this.next = null;

* }

* }

*/

public class Solution {

/**

* @param head: The first node of linked list.

* @param n: An integer.

* @return: The head of linked list.

*/

ListNode removeNthFromEnd(ListNode head, int n) {

// write your code here

ListNode x = head;

int count = 0;

while (x != null) {

count++;

x = x.next;

}

int asc = count - n;

ListNode res = new ListNode(-1000);

ListNode resx = res;

ListNode headx = head;

int i = 0;

while (headx.next != null) {

if(i == asc) {

headx = headx.next;

}else{

resx.next = headx;

resx = resx.next;

headx = headx.next;

}

i++;

}

if(i==asc){

resx.next = null;

}else{

resx.next = headx;

}

return res.next;

}

}