CC2.7_1.java

/*2.7  Implement a function to check if a linked list is a palindrome.*/

public class Solution {
    public boolean isPalindrome(ListNode head) {
        ListNode prehead = new ListNode(-1);
        prehead.next = null;
        ListNode l1 = head;
        while(l1!=null) {
            ListNode tmp = new ListNode(l1.val);
            tmp.next = prehead.next;
            prehead.next = tmp;
            l1 = l1.next;
        }
        prehead = prehead.next;
        while(head!=null && prehead!=null) {
            if(head.val!=prehead.vl) {
                return false;
            }
            head = head.next;
            prehead = prehead.next;
        }
        if(head!=null || prehead!=null)
            return false;
        return true;
    }
}