206-reverse-linked-list.md

206. Reverse Linked List - 反转链表

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

进阶:
你可以迭代或递归地反转链表。你能否用两种方法解决这道题？

---

题目标签：Linked List

题目链接：LeetCode / LeetCode中国

题解

Language	Runtime	Memory
cpp	8 ms	1.2 MB

/**
 * 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 || !head->next) { return head; }
        ListNode* p = head;
        ListNode* q = head->next;
        while (q->next) {
            ListNode* r = q->next;
            q->next = p;
            p = q;
            q = r;
        }
        q->next = p;
        head->next = NULL;
        return q;
    }
};