[Lintcode Medium] Palindrome Linked List

Palindrome Linked List

Implement a function to check if a linked list is a palindrome.

Example

Given 1->2->1 , return True

Challenge

Could do it in O (n) time and O (1) space?

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1\find out the medium index of Linked list

2\ reverse the right part of linked list in place

3\compare their value;

/*** Definition for singly-linked list. * public class ListNode {* int val; * ListNode Next; * ListNode (int X) {val = x;}}*/ Public classSolution {/**     * @paramhead a ListNode *@returna Boolean*/     Public BooleanIspalindrome (ListNode head) {//Write Your code here        if(head==NULL|| head.next==NULL)return true; if(head.next.next==NULL)        {            if(head.val==head.next.val)return true; Else return false; } ListNode Fast=Head; ListNode Slow=Head;  while(fast.next!=NULL&& fast.next.next!=NULL) {Fast=Fast.next.next; Slow=Slow.next; } ListNode head2=Slow.next; ListNode Pre=NULL; ListNode cur=head2; Slow.next=NULL;  while(cur!=NULL) {ListNode next=Cur.next; Cur.next=Pre; Pre=cur; Cur=Next; } head2=Pre; ListNode P=Head; ListNode Q=head2;  while(q!=NULL)        {            if(p.val==q.val) {p=P.next; Q=Q.next; }            Else             return false; }        return true; }

[Lintcode Medium] Palindrome Linked List