题目：定义一个函数，输入一个链表的头节点，反转该链表并输出反转链表的头节点。
#include <iostream> using namespace std; typedef struct listnode { int val; struct listnode* next; }ListNode; void creatList(ListNode** head) { int num; cin >> num; ListNode* tail = nullptr; while (num != -1) { ListNode* node = new ListNode; node->val = num; node->next = nullptr; if (*head == nullptr) { *head = node; tail = node; } else { tail->next = node; tail = node; } cin >> num; } } void reverseList(ListNode** head) { if (*head == nullptr || (*head)->next == nullptr) return; ListNode* rtail, *rsecond, *rhead; rtail = *head; rsecond = (*head)->next; rhead = (*head)->next; rtail->next = nullptr; while (rhead->next != nullptr) { rhead = rhead->next; rsecond->next = rtail; rtail = rsecond; rsecond = rhead; } rhead->next = rtail; *head = rhead; } int main() { ListNode* head = nullptr; creatList(&head); reverseList(&head); }
