题解 | #删除有序链表中重复的元素-II#

using System;
using System.Collections.Generic;

/*
public class ListNode
{
    public int val;
    public ListNode next;

    public ListNode (int x)
    {
        val = x;
    }
}
*/

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 null;
        ListNode lnRtn, ln;
        lnRtn = ln = new ListNode(0);
        int nPreVal = ln.val;
        while (head != null) {
            bool bVal = head.val != nPreVal && head.next != null &&
                        head.next.val != head.val;
            bVal = bVal || (head.val != nPreVal && head.next == null);
            if (bVal) {
                nPreVal = head.val;
                ListNode tmp = head.next;
                ln.next = head;
                head.next = null;
                head = tmp;
                ln = ln.next;
            } else {
                nPreVal = head.val;
                head = head.next;
            }
        }
        return lnRtn.next;
    }
}