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 ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    public ListNode deleteDuplicates (ListNode head) {
        ListNode dummy = new ListNode(1001), tail = dummy, p0 = new ListNode(1002), p = head;
        p0.next = p;

        while (p!=null) {
            if (p0.val!=p.val) {
                if (p.next==null || (p.next!=null && p.val!=p.next.val)) {
                    tail.next = p;
                    tail = p;
                }
            }
            p0 = p0.next;
            p = p.next;
        }

        tail.next = null;

        return dummy.next;
    }
}