题目

反转一个单链表。
示例:
输入: 1->2->3->4->5->NULL
输出: 5->4->3->2->1->NULL

解析

模板题，注意head为空的情况

代码

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* reverseList(ListNode* head) {
        if (!head) return NULL;
        ListNode* dummy = new ListNode(-1);
        dummy->next = head;
        ListNode* pre = dummy;
        ListNode* cur = dummy->next;
        while (cur->next) {
            ListNode* nxt = cur->next;
            cur->next = nxt->next;
            nxt->next = pre->next;
            pre->next = nxt;
        }
        return dummy->next;
    }
};