給定一個排序連結串列，刪除所有含有重複數字的節點，只保留原始連結串列中 沒有重複出現 的數字。

基本思路是第一層迴圈，兩個指標分別指向當前元素和它的前繼，目的是如果有重複，需要刪除當前元素，然後直到當前元素為空

第二層迴圈，兩個指標分別指向當前元素的下一個元素和它的前繼，目的是如果有重複，需要刪除當前元素之後的所有元素，然後直到當前比較元素為空

ListNode* Solution::deleteDuplicates(ListNode* head)
{
    ListNode *pnewhead = new ListNode(0);
    ListNode *pcurrentlast = pnewhead;
    ListNode *pcurrent = head;
    unsigned int DuplicateFlag = 0;
    
    if((head == NULL)||(head->next == NULL))
    {
        return head;
    }
    pcurrentlast->next = head;
    while(pcurrent != NULL)
    {
        ListNode *pnext = pcurrent->next;
        ListNode *pnextlast = pcurrent;
        while(pnext != NULL)
        {
            if(pnext->val == pcurrent->val)
            {
                DuplicateFlag = 1;
                pnextlast->next = pnext->next;
                pnext = pnext->next;
            }
            else
            {
                pnext = pnext->next;
                pnextlast = pnextlast->next;
            }
        }
        /*no data duplicate*/
        if(0 == DuplicateFlag)
        {
            pcurrent = pcurrent->next;
            pcurrentlast = pcurrentlast->next;
        }
        else
        {
            /*data duplicate,delete current node*/
            pcurrentlast->next = pcurrent->next;
            pcurrent = pcurrent->next;
            DuplicateFlag = 0;
        }
    }
    return pnewhead->next;
}