今天真是吓死宝宝了

作为一个弱鸟菜鸟蜻蜓点水鸟，竟然今天AC出来个100%胜出，有点晕头转向=。=

吓死了.png

206. Reverse Linked List

Reverse a singly linked list.
A linked list can be reversed either iteratively or recursively. Could you implement both?
也是得益于Discuss的启发。现在把我理解后自己写的代码展出：

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

554811933326058546.jpg

写代码还是需要纸和笔

链表这东西，我在脑袋上都没搞清楚怎么翻转，那代码更不可能了。后来发现纸笔验算下还是可以的，说白了还是我的脑袋的内存不够，不够验算的~