TOP101题解|BM16#删除有序链表中重复的元素-II#

#define illegalVariable 1001
/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */
/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 * @author Senky
 * @date 2023.04.23
 * @par url https://www.nowcoder.com/creation/manager/content/584337070?type=column&status=-1
 * @param head ListNode类 
 * @return ListNode类
 */
struct ListNode* deleteDuplicates(struct ListNode* head ) {
    // write code here
    struct ListNode* pre = NULL;//前指针
    struct ListNode* cur = NULL;//现指针
    int illegal[1] = {illegalVariable};//记录要处理的结点值,默认是非法值

    if(head)
    {
        pre = head;
        illegal[0] = pre->val;
        cur = head->next;
    }
    /*把每个一样的结点数据域都修改成一个非法值*/
    while(pre && cur)
    {
        if(cur->val != illegal[0])
        {
            illegal[0] = cur->val;//现结点值不等于上一个结点值,现结点值录入数组
        }
        else 
        {
            /*现节点值等于上一个结点值,两个结点都设为非法*/
            pre->val = illegalVariable;
            cur->val = illegalVariable;
        }
        pre = pre->next;
        cur = cur->next;
    }
    /*把非法值的节点删除*/
    {
        struct ListNode* legal = head;//上一个合法的结点,默认头
        cur = head;
        while(cur)
        {
            if(illegalVariable == cur->val)
            {
                if(cur == head)
                {
                    head = head->next;
                }
                else 
                {
                    legal->next = cur->next;
                }
            }
            else 
            {
                legal = cur;
                
            }
            cur = cur->next;
        }
    }

    return head;
}