/**

* Definition for singly-linked list.

* struct ListNode {

* int val;

* struct ListNode *next;

* };

*/

struct ListNode * reverse(struct ListNode *head) {

struct ListNode *res = NULL;

while(head) {

struct ListNode *pre_node = head;

head = head -> next;

pre_node ->next = res;

res = pre_node;

}

return res;

}

bool isPalindrome(struct ListNode* head){

struct ListNode *slow = head;

struct ListNode *fast = head;

struct ListNode *last;

while (fast && fast->next) {

slow = slow -> next;

fast = fast -> next -> next;

}

if(fast != NULL)

slow = slow -> next;

last = reverse(slow);

while(last) {

if (head->val != last->val)

return 0;

head = head -> next;

last = last -> next;

}

return 1;

}