Question

public boolean isPalindrome()
{

    Stack myStack = new Stack();
    for(Node current = head; current!=null; current = current.next)
    {
        if(!myStack.isEmpty())
        {
            if(myStack.peek()==current.data)
            {
                myStack.pop();
            }else if(current.next!=null&&myStack.peek()==current.next.data)
            {
                continue;
            }
            else
            {
                myStack.push(current.data);
            }
        }else
        {

            myStack.push(current.data);
        }   

    }

    return myStack.isEmpty();
}

What I am doing here is using a stack to check whether a linked list is a palindrome. It works as expected only thing is I wanted to get rid of code duplication where the else condition has a push of the data onto the stack.

Answer 1

The algorithm is unfortunately not correct. For “abbaaa” it would report that that is a palindrome, although it isn’t. Checking for palindromes without using the length is difficult.

abbaaa () -> push a
bbaaa (a) -> push b
baaa (ba) -> pop b
aaa (a) -> pop a
aa () -> push a
a (a) -> pop a
() -> palindrome