【leetcode刷题笔记】Remove Nth Node From End of List

   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.

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     int val;
 5  *     ListNode next;
 6  *     ListNode(int x) {
 7  *         val = x;
 8  *         next = null;
 9  *     }
10  * }
11  */
12 public class Solution {
13     public ListNode removeNthFromEnd(ListNode head, int n) {
14         if(head == null)
15             return null;
16         
17         ListNode slow = new ListNode(0);
18         ListNode answer = slow;
19         slow.next = head;
20         ListNode fast = head;
21         for(int i = 0;i < n;i++){
22             if(fast == null)
23                 return null;
24             fast = fast.next;
25         }
26         while(fast != null){
27             slow = slow.next;
28             fast = fast.next;
29         }
30         
31         //delete what slow.next
32         slow.next = slow.next.next;
33         return answer.next;
34     }
35 }