19. 删除链表的倒数第 N 个结点

/**
 * 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) {
        //注意初始化
        int s_fast = 1;
        ListNode dummyhead = new ListNode();
        dummyhead.next = head;
        ListNode fast = dummyhead;
        ListNode slow = dummyhead;
        while(fast!=null){
            fast = fast.next;
            if (s_fast++<=n+1){
                continue;
            }else{
                slow = slow.next;
            }    
        }
        ListNode temp = slow.next.next;
        slow.next = temp;
        return dummyhead.next;

    }
}