Palindrome Linked List

Given a singly linked list, determine if it is a palindrome.

Follow up:
Could you do it in O(n) time and O(1) space?

 1 /**

 2  * Definition for singly-linked list.

 3  * struct ListNode {

 4  *     int val;

 5  *     ListNode *next;

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

 7  * };

 8  */

 9 class Solution {

10 public:

11     bool isPalindrome(ListNode* head) {

12         

13         vector<int> tmp;

14         while(head)

15         {

16             tmp.push_back(head->val);

17             head=head->next;

18         }

19         int left=0;

20         int right=tmp.size()-1;

21         while(left<right)

22         {

23             if(tmp[left]!=tmp[right])

24               return false;

25             left++;

26             right--;

27         }

28         return true;

29     }

30 };