/**

  * Definition for singly-linked list.

  * struct ListNode {

  *     int val;

  *     ListNode *next;

  *     ListNode(int x) : val(x), next(NULL) {}

  * };

  */

 class Solution {

 public:

     bool isPalindrome(ListNode* head) {

         if(head==NULL) return true;

         ListNode* cur=head;

         vector<int> ivec;

         while(cur){

             ivec.push_back(cur->val);

             cur=cur->next;

         }

         for(int i=;i<ivec.size()--i;i++){

             int j=ivec.size()--i;

             if(ivec[i]!=ivec[j]) return false;

         }

         return true;

     }

 };

 /**

  * Definition for singly-linked list.

  * struct ListNode {

  *     int val;

  *     ListNode *next;

  *     ListNode(int x) : val(x), next(NULL) {}

  * };

  */

 class Solution {

 public:

     bool isPalindrome(ListNode* head) {

         if(head==NULL||head->next==NULL) return true;

         ListNode* cur,*pre;

         cur=head;

         int length=;

         while(cur!=NULL){

             length+=;

             cur=cur->next;

         }

         cur=head->next;pre=head;head->next=NULL;

         for(int i=;i<(length+)/;i++){

                 ListNode* temp;

                 temp=cur->next;

                 cur->next=pre;

                 pre=cur;

                 cur=temp;

         }

         if(length%==) pre=pre->next;

         while(cur!=NULL){

             if(cur->val==pre->val){

                 cur=cur->next;pre=pre->next;

             }

             else return false;

         }

         return true;

     }

 };