题目描述

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

题解

/**
 * 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) {
        ListNode* pre = NULL, *next = NULL;
        while(head != NULL) {
            next = head->next;
            head->next = pre;
            pre = head;
            head = next;
        }
        return pre;
    }
};