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
        Set<Integer> set = new TreeSet<>();
        while(true) {
            if(head == null) break;
            set.add(head.val);
            head = head.next;
        }
        if(set.isEmpty()) return null;

        ListNode a = null;
        ListNode tail = null;
        for(int v: set) {
            if(a == null) {
                a = new ListNode(v);
                tail = a;
            } else {
            tail.next = new ListNode(v);
            tail = tail.next;
            }
        }
        return a;
    }
}