11. 怎样检测链表是否存在循环(只读内存,内存有限)解法:快慢指针法(Floyd 判圈法) struct Node { int val; struct Node *next; }; int has_cycle(struct Node* head) { struct Node *slow = head, *fast = head; while (fast && fast->next) { slow = slow->next; fast = fast->next->next; ...