/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* deleteDuplication(ListNode* head) {
        if(!head) return NULL;

        int numbers[110] = {0};

        for(ListNode* i = head; i != NULL; i = i->next)
            numbers[i->val]++;

        ListNode* fake = new ListNode(-1);
        fake->next = head;

        ListNode* i = fake;
        while (i != NULL) {
            while (i->next != NULL && numbers[i->next->val] > 1) {
                i->next = i->next->next;
            }
            i = i->next;
        }
        return fake->next;
    }
};