【求大神指教】C语言链表，长度判断，使用node->next == NULL) 为判断条件会超时

Question

struct ListNode *getIntersectionNode(struct ListNode *headA, struct ListNode *headB) 
{
    struct ListNode *tmp1 = headA;
    struct ListNode *tmp2 = headB;
    while (tmp1 != tmp2) {
        if (tmp1->next == NULL) {   //超时 
            tmp1 = headB;
        } else {
            tmp1 = tmp1->next;
        }
        if (tmp2->next == NULL) {
            tmp2 = headA;
        } else {
            tmp2 = tmp2->next;
        }
    }
    return tmp1;
}

下面代码正常运行，为什么呢？

struct ListNode *getIntersectionNode(struct ListNode *headA, struct ListNode *headB) 
{
    struct ListNode *tmp1 = headA;
    struct ListNode *tmp2 = headB;
    while (tmp1 != tmp2) {
        if (tmp1 == NULL) {   //为什么这里if (tmp1->next == NULL) 会超时？ 
            tmp1 = headB;
        } else {
            tmp1 = tmp1->next;
        }
        if (tmp2 == NULL) {
            tmp2 = headA;
        } else {
            tmp2 = tmp2->next;
        }
    }
    return tmp1;
}

Answer 1

有没有这种可能：

headA->NULL<-headB

这不是单线的链表了，但是可以重现你的错误。