LeetCode(19) － Remove Nth Node From End of List

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     int val;
 5  *     ListNode next;
 6  *     ListNode(int x) { val = x; }
 7  * }
 8  */
 9 public class Solution {
10     public ListNode removeNthFromEnd(ListNode head, int n) {
11         //当可能需要处理head的时候，用dumpNode来指向head，处理起来会方便很多。
12         ListNode dumpNode = new ListNode(0);
13         dumpNode.next = head;
14         ListNode prev = dumpNode;
15         ListNode curr = prev;
16         //让prev和curr的距离为n
17         while (n-- > 0) {
18             curr = curr.next;
19         }
20         //让curr走到链表尾部，prev随着curr一起走，
21         while (curr.next != null) {
22             prev = prev.next;
23             curr = curr.next;
24         }
25         //删除prev的下一个链表。
26         prev.next = prev.next.next;
27         //返回head。
28         return dumpNode.next;
29     }
30 }