Nth to Last Node in List

Find the nth to last element of a singly linked list. 

The minimum number of nodes in list is n.

Have you met this question in a real interview? 

Yes

Example

Given a List  3->2->1->5->null and n = 2, return node  whose value is 1.

快慢指针，让快指针先走n - 1次，然后快慢指针一起走，当fast == null 的时候，说明slow的位置就是所求的结果。

代码：

ListNode nthToLast(ListNode head, int n) {        // write your code here        if(head == null) return null;        ListNode fast = head;        ListNode slow = head;        int count = 1;        while(count<n && fast.next != null)        {            fast = fast.next;            count++;        }        while(fast.next != null){            slow = slow.next;            fast = fast.next;        }        return slow;    }