题解 | #删除有序链表中重复的元素-II# O(1)空间

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
        ListNode hair = new ListNode(0);
        ListNode pointer = hair;
        ListNode it = head;
        int current = 1001;
        while (it != null) {
            if (it.next != null && it.val == it.next.val) {
                current = it.val;
            }
            if (it.val == current) {
                it = it.next;
                continue;
            }
            pointer.next = it;
            it = it.next;
            pointer = pointer.next;
        }
        pointer.next = null;
        return hair.next;
    }
}