[leetcode]-234. Palindrome Linked List（C语言）

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

Example 1:

Input: 1->2
Output: false

Example 2:

Input: 1->2->2->1
Output: true

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

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
bool isPalindrome(struct ListNode* head) {
    if(head==NULL||head->next==NULL)
        return true;
    struct ListNode *p=head;
    int a[100000],i=0,j=0,k;
    while(p->next!=NULL)
    {
        a[i++]=p->val;
        p=p->next;
    }
    a[i]=p->val;
    while(j