Problem2-7.java

class Node {
  Node next;
  Node prev;
  int data;
  
  public Node(int value) {
    this.data = value;
  }
}

public boolean isPalindrome(Node head) {
  if (head == null)
    return false;
    
  Node tail;
  Node node = head;
    
  while (node != null) {
    Node prev = node;
    node = node.next;
    if (node != null) {
      node.prev = prev;
    }
    else {
      tail = prev;
    }
  }
  
  while (head != tail && tail.next != head) {
    if (head.data == tail.data) {
      head = head.next;
      tail = tail.prev;
    }
    else
      return false;
  }
  
  return true;
}