题解 | #反转链表#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 *	ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
#include <cstddef>
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) {
            return nullptr;
        } else {
            ListNode* pre = nullptr;
            ListNode* next = nullptr;
            while(head != nullptr) {
                next = head->next;
                head->next = pre;
                pre = head;
                head = next;
            }
            return pre;
        }
    }
};