单链表相关操作

struct ListNode {
    int val;
    ListNode *next;
};

ListNode* createListFromHead()
{
    ListNode *list = (ListNode*)malloc(sizeof(ListNode));
    list->next = NULL;
    ListNode *s;
    int x;
    while (cin >> x)
    {
        s = (ListNode*)malloc(sizeof(ListNode));
        s->val = x;
        s->next = list->next;
        list->next = s;
    }
    return list;
}

ListNode* createListFromTail()
{
    ListNode *list = (ListNode*)malloc(sizeof(ListNode));
    list->next = NULL;
    ListNode *s;
    int x;
    ListNode *p = list;
    while (cin >> x)
    {
        s = (ListNode *)malloc(sizeof(ListNode));
        s->val = x;
        p->next = s;
        p = s;
    }
    p->next = NULL;
    return list;
}