数据结构编写代码，利用带头结点单链表原来的节点空间逆转一个单链表

void reverseList(Node* head) {
    if (head == nullptr || head->next == nullptr) {
        return;
    }
    Node* pre = head->next;
    Node* cur = pre->next;
    pre->next = nullptr;
    while (cur != nullptr) {
        Node* next = cur->next;
        cur->next = pre;
        pre = cur;
        cur = next;
    }
    head->next = pre;
}