Nth to Last Node in List

41% Accepted

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.

Tags Expand

• Cracking The Coding Interview
• Linked List

思路

• dummy listnode

/**
 * 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) {
        // write your code here
        if (head == null) {
            return null;
        }
        ListNode fast = new ListNode(0);
        fast.next = head;
        head = fast;
        ListNode slow = head;
        while (fast.next != null && n > 0) {
            n--;
            fast = fast.next;
        }
        while (fast.next != null) {
            fast = fast.next;
            slow = slow.next;
        }
        return slow.next;
    }
}