移除链表元素

法一：在原链表上删除

struct SListNode* removeElements(struct SListNode* head, int val)
{
    if (head == NULL)
        return NULL;
    while (head->data == val)
    {
        struct SListNode* del = head;
        head = del->next;
        free(del);
        del = NULL;
        if (head == NULL)
            break;
    }
    if (head == NULL)
        return NULL;
    struct SListNode* cur = head;
    
    while (cur->next != NULL)
    {
        if (cur->next->data == val)
        {
            struct SListNode* del = cur->next;
            cur->next = del->next;
            free(del);
            del = NULL;
        }
        else
        {
            cur = cur->next;
        }
    }
    return head;
}

法二:创建新的链表

struct SListNode* removeElements(struct SListNode* head, int val)
{
    struct SListNode* pcur = NULL, * pend = NULL;
    struct SListNode* cur = head;
    if (cur == NULL)
        return NULL;
    else
    {
        while (cur != NULL)
        {
            if (cur->data != val)
            {
                if (pcur == NULL)
                    pcur = pend = cur;
                else
                {
                    pend->next = cur;
                    pend = cur;
                }
            }
            cur = cur->next;
        }
        if (pend != NULL)
            pend->next = NULL;
        head = pcur;
        return head;
    }
}