/**

 * Definition for singly-linked list.

 * struct ListNode {

 *     int val;

 *     struct ListNode *next;

 * };

 */

struct ListNode* reverseList(struct ListNode* head) {

    if(!head||!head->next)

        return head;

    struct ListNode *cur=head;

    struct ListNode *tail=head;

    while(tail->next)

        tail=tail->next;

    while(cur!=tail)

    {

        head=cur->next;

        cur->next=tail->next;

        tail->next=cur;

        cur=head;

    }

    return head;

}

struct ListNode* reverseList(struct ListNode* head) {

    if(head&&head->next)

    {

        struct ListNode* pre=NULL;

        struct ListNode* cur=head;

        struct ListNode* pnext=cur->next;

        while(pnext)

        {

            cur->next=pre;

            pre=cur;

            cur=pnext;

            pnext=cur->next;

        }

        cur->next=pre;

        head=cur;

    }

    return head;

}