import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代碼中的類名、方法名、參數(shù)名已經(jīng)指定，請(qǐng)勿修改，直接返回方法規(guī)定的值即可
     *
     *
     * @param head ListNode類
     * @return ListNode類
     */
    public ListNode deleteDuplicates (ListNode head) {
        // write code here
        if (head == null) {
            return null;
        }
        if (head.next == null) {
            return head;
        }
        ListNode nHead = new ListNode(-1);
        nHead.next = head;
        ListNode cur = nHead;
        while (cur.next != null && cur.next.next != null) {
            if (cur.next.val == cur.next.next.val) {
                int tmp = cur.next.val;
                while (cur.next != null && tmp == cur.next.val) {
                    cur.next = cur.next.next;
                }
            } else {
                cur = cur.next;
            }
        }
        return nHead.next;
        //為什么設(shè)置頭節(jié)點(diǎn),因?yàn)榈谝粋€(gè)節(jié)點(diǎn)可能被刪除
    }
}