LeetCode每日一题：remove duplicates from sorted list ii

问题描述

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.
For example,
Given1->2->3->3->4->4->5, return1->2->5.
Given1->1->1->2->3, return2->3.

问题分析

对于这题，一旦发现有重复的节点，连同它本身也要删除，所以我们要新建一个辅助节点用来保存结点的前一个节点。

代码实现

public ListNode deleteDuplicates(ListNode head) {
        if (head == null || head.next == null) return head;
        ListNode preNode = new ListNode(0);
        ListNode curNode = head;
        preNode.next = head;
        ListNode node = preNode;
        while (curNode != null && curNode.next != null) {
            if (curNode.val != curNode.next.val) {
                node = curNode;
            } else {
                while (curNode.next != null && curNode.val == curNode.next.val) {
                    curNode = curNode.next;
                    node.next = curNode.next;
                }
            }
            curNode = curNode.next;
        }
        return preNode.next;
    }