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) {
        int[] cnt = new int[2001];
        ListNode res = new ListNode(0);
        res.next = head;
        ListNode p = head;
        ListNode q = res;
        while (head != null) {
            cnt[head.val+1000]++;
            head = head.next;
        }
        while (p != null) {
            if (cnt[p.val+1000] > 1) {
                ListNode next = p.next;
                p.next = null;
                q.next = next;
                p = next;
            } else {
                q = p ;
                p = p.next;
            }
        }
        return res.next;
    }
}