Leetcode 206 Reverse Linked List

Reverse a singly linked list.

链表逆置，之前好像做过类似的Leetcode题目了。

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