leetcode hot 24

解题思路：这题的思路就是让一个指针先走n步，然后再用另一个指针同步走，直到先走的指针的next为null，然后后面的指针的后一个指针删掉即可。

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode fast = new ListNode(0,head);
        ListNode slow  = new ListNode(0,head);
        ListNode q = slow;
        while(n>0){
            fast = fast.next;
            n--;
        }
        while(fast.next!=null){
            fast = fast.next;
            slow = slow.next;
        }
        slow.next = slow.next.next;
        return q.next;
    }
}