在一个排序的链表中，存在重复的结点，请删除该链表中重复的结点，重复的结点不保留。 例如，链表1->2->3->3->4->4->5 处理后为 1->2->3->4->5,用c语言写代码。

struct ListNode* deleteDuplication(struct ListNode* pHead)
{
    if(pHead == NULL || pHead->next == NULL)
        return pHead;

    struct ListNode* pPreNode = NULL;
    struct ListNode* pNode = pHead;
    while(pNode != NULL)
    {
        struct ListNode* pNext = pNode->next;
        bool needDelete = false;
        if(pNext != NULL && pNode->val == pNext->val)
            needDelete = true;

        if(!needDelete)
        {
            pPreNode = pNode;
            pNode = pNode->next;
        }
        else
        {
            int val = pNode->val;
            struct ListNode* pToBeDel = pNode;
            while(pToBeDel != NULL && pToBeDel->val == val)
            {
                pNext = pToBeDel->next;

                free(pToBeDel);
                pToBeDel = NULL;

                pToBeDel = pNext;
            }

            if(pPreNode == NULL)
                pHead = pNext;
            else
                pPreNode->next = pNext;

            pNode = pNext;
        }
    }

    return pHead;
}