题解 | #反转链表#

/**
 * struct ListNode {
 *  int val;
 *  struct ListNode *next;
 *  ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param head ListNode类
     * @return ListNode类
     */
    ListNode* ReverseList(ListNode* head) {
        // write code here
        if (head == nullptr || head->next == nullptr) {
            return head;
        }
        //创建一个临时头节点
        ListNode* pHead = new ListNode(0);
        ListNode* p = head;
        ListNode* q = head;
        //依次执行头插操作
        while (p != nullptr) {
            p = q->next;
            q->next = pHead->next;
            pHead->next = q;
            q = p;
        }
        head = pHead->next;
        delete pHead;
        return head;
    }
};