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.

Example

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

分析：

要找到nth to last element，我们需要两个指针，第一个指针先走n步，然后两个指针同时走，知道第一个指针为null.

public class Solution {
    /**
     * @param head: The first node of linked list.
     * @param n: An integer.
     * @return: Nth to last node of a singly linked list. 
     */
    ListNode nthToLast(ListNode head, int n) {
        if (head == null || n <= 0) return null;
        
        ListNode first = head;
        ListNode last = head;

        for (int count = 1; count <= n; count++;) {
            first = first.next;
        }
        
        while(first != null) {
            first = first.next;
            last = last.next;
        }
        return last;
    }
}

转载请注明出处：cnblogs.com/beiyeqingteng/