82 Remove Duplicates from Sorted List 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.

/**
 * 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) {
        ListNode* dummy =new ListNode(0);
        dummy->next = head;
        int val = INT_MIN;
        ListNode *cur = head;
        ListNode* pre = dummy;
        while(cur)
        {
            if (cur->val == val || cur->next && cur->val == cur->next->val)
            {
                pre->next = cur->next;
                val = cur->val;
                delete cur;
                cur=pre->next;
            }
            else
            {
                val = cur->val;
                pre = cur;
                cur = cur->next;
            }
        }
        head = dummy->next;
        delete dummy;
        return head;
    }
};