题解 | #删除有序链表中重复的元素-I#

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) {
        // write code here
        if(head==null){
            return head;
        }
        Set<Integer> set = new HashSet<>();
        ListNode cur = head.next;
        ListNode pre = head;
        set.add(head.val);
        while(cur!=null){
            if(set.contains(cur.val)){
                cur = cur.next;
                pre.next = cur;
            }else{
                set.add(cur.val);
                cur = cur.next;
                pre = pre.next;
            }
        }
        return head;
    }
}