题解 | #删除有序链表中重复的元素-II#

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 * }
 */

public class Solution {
    /**
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    public ListNode deleteDuplicates (ListNode head) {

        if (head == null) {
            return head;
        }

        ListNode headNode = new ListNode(-1);
        headNode.next = head;
        ListNode preNode = headNode;
        ListNode curNode = head;

        while (curNode != null && curNode.next != null) {

            if (curNode.val == curNode.next.val) {

                while (curNode.next != null && curNode.val == curNode.next.val) {

                    curNode = curNode.next;
                }

                preNode.next = curNode.next;
                curNode = curNode.next;
            } else {

                preNode = curNode;
                curNode = curNode.next;
            }
        }

        return headNode.next;
    }
}