LeetCode OJ：Remove Duplicates from Sorted List II（链表去重II）

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

For example,
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

这里对于链表去重是要将有重复的链表节点全部都去掉，一个都不能留，思路还是比较简单的，跟前面的I那一题实际上差不多，代码如下所示：

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        if(!head) return NULL;
        ListNode * helper = new ListNode(INT_MAX);
        helper->next = head;
        ListNode * prev = helper;
        ListNode * curr = head;
        while(curr){
            if(curr->next && curr->val == curr->next->val){
                ListNode * tmpNode = curr->next;
                while(tmpNode->next && curr->val == tmpNode->next->val){
                    tmpNode = tmpNode->next;
                }
                prev->next = tmpNode->next;
                curr = prev->next;
            }else{
                prev = curr;
                curr = curr->next;
            }
        }
        return helper->next;
    }
};