[剑指offer] 56. 删除链表中重复的结点

class Solution
{
  public:
    ListNode *deleteDuplication(ListNode *pHead)
    {
        if (pHead == NULL || pHead->next == NULL)
            return pHead;

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

        ListNode *p = head;
        ListNode *q = head->next;
        while (q)
        {
            while (q->next && (q->next->val == q->val))
            {
                q = q->next;
            }
            if (p->next != q)
            {
                q = q->next;
                p->next = q;
            }
            else
            {
                p = q;
                q = q->next;
            }
        }
        return head->next;
    }
};