Singly linked list palindrome

[flav32]

I have to check if a singly linked list forms a palindrome of characters. Each node keeps a character.
I can't use a double linked list. With the code I wrote I'm getting this on a few tests -1073741819 (0xC0000005)
I also get a warning : control reaches end of non-void function. I don't understand what I'm doing wrong...

  bool palindrome(node *head)
{   node*last=head->next->next;  //last gets this value so we can enter the 
                                    while loop
    node* first=head;

    while(first->next!=last && first!=last)
        { last=first;
            while(last->next)
             last=last->next;   //getting the last value in the list

            if(last->info!=first->info)
                return false;              //end function if the list is not a 
                                              palindrome
            else
            {                           
                node* first_del=first;   //if first and last are equal, I 
                first=first_del->next;  //delete both of them so I can check
                delete first_del;       //if the next elements in the list make 
                                        //up a palindrome

                node*del=last;
                last=NULL;
                delete del;

            }

          }
        if(first->next==last && first->next->info==last->info)
                return true;
                else if(first==last)
                       return true;
    }


//if all nodes to the middle of the list were deleted, and the value/s in the middle are still equal, the list is a palindrome.

[jonnin]

control reaches end of non-void function
- a function which has a type (like int foo() ) did not contain a return statement or the return statement is inside a condition and the other path is missing one, etc.


being lazy, I have to note that:
-insert at head of a list is simple. It happens to reverse the input naturally.
- you already have the input string.
- if you were to, I dunno, iterate the list forwards comparing against the string's letters, it would tell you the answer using the above 2 bullets.
- you can also just insert 1/2 the chars then check what is left against what you put in, again using the insert at top reversal idea.

I don't see your bug.

[dhayden]

You're deleting the nodes in the list as you go. Is it really okay for palindrome() to destroy the list that's passed into it?

Line 2: this will crash if the list has 0 or 1 items.
Line 23: you delete the last node, but the previous node still points to it.

I'm thinking that the algorithm is wrong here. I suspect that there's an easy way to do it with recursion.

[flav32]

I don't care about the list as I only have to make this function work, but I can see why it's a bad practice. The list must have at least 3 nodes so that's not a problem either.
What I thought I was doing at line 23 was that after I deleted the last node, the last but one would be the "new last" node and the function would keep going. I'm going to try recursion too. Thanks a lot!