Leetcode82. Remove Duplicates from Sorted List II删除排序链表中的重复元素2

给定一个排序链表，删除所有含有重复数字的节点，只保留原始链表中 没有重复出现 的数字。

示例 1:

输入: 1->2->3->3->4->4->5 输出: 1->2->5

示例 2:

输入: 1->1->1->2->3 输出: 2->3

新设置一个头节点

class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head)
    {
        if(head == NULL)
            return head;
        ListNode* newHead = new ListNode(0);
        newHead ->next = head;
        ListNode* last = newHead;
        ListNode* current = head;
        ListNode* next = head ->next;
        while(next)
        {
            if(next ->val == current ->val)
            {
                while(next && next ->val == current ->val)
                {
                    next = next ->next;
                }
                if(next)
                {
                    current = next;
                    next = next ->next;
                    last ->next = current;
                }
                else
                    last ->next = next;
            }
            else
            {
                last ->next = current;
                last = last ->next;
                current = next;
                next = next ->next;
            }
        }
        return newHead ->next;
    }
};