Q20 LeetCode19 删除链表倒数第N个节点

1.创建虚拟头结点ListNode pre=new ListNode(0,head);

2.创建快慢节点

3.快节点fastIndex先往后移N个位置

4.快慢slowIndex节点一直往后移，直至快节点到链表末尾

5.删除慢节点后面的节点

 1 class Solution {
 2     public ListNode removeNthFromEnd(ListNode head, int n) {
 3         ListNode pre=new ListNode(0,head);
 4         ListNode fastIndex=pre;
 5         ListNode slowIndex=pre;
 6         for(int i=0;i<n;i++){
 7             fastIndex=fastIndex.next;
 8         }
 9         while(fastIndex.next!=null){
10             fastIndex=fastIndex.next;
11             slowIndex=slowIndex.next;
12         }
13         if(slowIndex.next!=null){
14             slowIndex.next=slowIndex.next.next;
15         }
16         return pre.next;
17 
18     }
19 }