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.

/**
 * Definition for ListNode.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int val) {
 *         this.val = val;
 *         this.next = 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) {
            return null;
        }
        ListNode front = head;
        ListNode node = head;
        while (n > 0) {
            if (front == null) {
                return null;
            }
            front = front.next;
            n--;
        }
        while (front != null) {
            node = node.next;
            front = front.next;
        }
        return node;
    }
}