力扣 LeetCode 19. 删除链表的倒数第N个结点（Day2：链表）
解题思路：
快慢指针
class Solution {
public ListNode removeNthFromEnd(ListNode head, int n) {
ListNode dummy = new ListNode(-1);
dummy.next = head;
ListNode fast = dummy;
ListNode slow = dummy;
for (int i = 0; i < n; i++) {
fast = fast.next;
}
while (fast.next != null) {
fast = fast.next;
slow = slow.next;
}
slow.next = slow.next.next;
return dummy.next;
}
}