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) {
        if (head == null || head.next == null) {
            return head;
        }
        // 记录删减后的节点
        ListNode res = new ListNode(-101);
        // 记录前一个节点
        ListNode dump = res;
        while (head != null) {
            int dumpValue = dump.val;
            int headValue = head.val;
            ListNode next = head.next;
            head.next = null;
            // 当前节点和上一个节点值不相等，添加到上一个节点后面
            if (dumpValue != headValue) {
                dump.next = head;
                dump = dump.next;
            }
            head = next;
        }
        return res.next;
    }
}