Question

So I’m in a summer OO class and we need to write a function to delete a node from the middle of a linked list. I’m really close but there are a few problems. My code iterates through the linked list successfully but there is trouble actually deleting the node once the loop finds the node. Here’s my function so far:

template< class NODETYPE >
bool List< NODETYPE >::removeMiddle( NODETYPE &value, int i )
{
    ListNode <NODETYPE> * tempPtr = firstPtr;
    ListNode <NODETYPE> * prevPtr ;
    int counter=1;

    if ( isEmpty() )
        return false;
    if (i <= 0)
        return false;

    while (tempPtr != 0 && counter < i){
        counter++;
        if ( firstPtr == lastPtr )
        firstPtr = lastPtr = 0;
    else
        firstPtr = firstPtr->nextPtr;
            prevPtr = tempPtr;
            tempPtr = tempPtr->nextPtr;
        }

        if (counter == i){
            value = tempPtr->data;  // data being removed
            delete tempPtr;
        }
    }

    return true;
    RecordCounter--;
}

Answer 1

You forgot to change the previous node so that it no longer points to the node you delete.

You want something (largely) similar to:

if ( counter == i-1 ) //next node is the one you want to delete
{
    aux = tempPtr->nextPtr->nextPtr;   //retain next next node
    delete tempPtr->nextPtr;           //delete next node
    tempPtr->nextPtr = aux;            //current node now points to the node after the deleted one
}