LeetCode : Palindrome Linked List

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

/**
 * 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) {
        vector<int>vec;
        ListNode *p = head;
        int count = 0;
        while(p)
        {
            count++;
            p=p->next;
        }
        p = head;
        if(count%2==0)
          {
              count/=2;
              while(count--)
              {
                  vec.push_back(p->val);
                  p=p->next;
              }
          }
         else
         {
             count/=2;
             while(count--)
             {
                 vec.push_back(p->val);
                 p=p->next;
             }
             p=p->next;
         }
       reverse(vec.begin(),vec.end());
       int i = 0;
       while(p)
       {
           if(p->val!=vec[i])
              return false;
            p=p->next;
            ++i;
       }
       return true;
    }
};