problem:

Reverse a singly linked list.

Hint:

A linked list can be reversed either iteratively or recursively. Could you implement both?

solution:头插法逆转链表

/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */ //头插法逆转链表class Solution {public:    ListNode* reverseList(ListNode* head) {        ListNode result(-1);               ListNode *cur=head;        while(cur!=NULL)        {            ListNode *nnode=new ListNode(cur->val);            nnode->next=result.next;            result.next=nnode;                   cur=cur->next;        }        return result.next;    }};