2 functions

Test.cpp

SparseArrayNode *SparseArray::getPreviousNode(int index)
{
    // if null or current index is greater than head index
    cout << endl;
    cout << "current node INDEX " << index << endl;
    if (headPtr != NULL)
    {
        cout << "prev node HEAD INDEX " << headPtr->index << endl;
    }
    cout << endl;

    if (headPtr == NULL || headPtr->index >= index)
    {
        cout << "STOP" << endl;
        return NULL;
    }
    // assign head to cursor
    SparseArrayNode *pNode = headPtr;
    // create temp store
    SparseArrayNode *previous = NULL;
    while (pNode != NULL)
    {
        // if index is greater, than previous was less
        cout << "current is  " << pNode->index << endl;
        if (previous)
            cout << "previous is" << previous->index << endl;

        if (pNode->index > index)
        {
            cout << "HERE " << pNode->index << endl;
            // cout << "previous is " << previous->index << endl;
            return previous;
        }
        // track previous so it can be returned
        previous = pNode;
        // move to next node
        pNode = pNode->next;
    }
}


void SparseArray::insert(int index, const string &value)
{
    // assert(invariant());
    if (headPtr == NULL)
    {
        cout << "HERE" << endl;
        SparseArrayNode *s = new SparseArrayNode();
        s->value = value;
        s->index = index;
        s->next = NULL;
        headPtr = s;
        return;
    }
    if (value != default_value)
    {
        // check if node index exists
        SparseArrayNode *existingNode = getExactNode(index);
        // if it does, change the value
        if (existingNode)
        {
            existingNode->value = value;
        }
        else
        {
            // get previous node
            SparseArrayNode *previousNode = getPreviousNode(index);
            cout << "prev node val " << previousNode << endl;
            if (previousNode != NULL)
            {
                // cout << "prev node val " << previousNode->value << endl;
                SparseArrayNode *s = new SparseArrayNode();
                s->index = index;
                s->value = value;
                // point new node at what previous node pointed to
                s->next = previousNode->next;
                // point previous at new node
                previousNode->next = s;
            }
            else
            // if only one node, so no previous
            {
                SparseArrayNode *s = new SparseArrayNode();
                cout << "bottom of insert here " << endl;
                s->index = index;
                s->value = value;
                //SEG FAULT HERE
                s->next = headPtr->next;
                // make s new head
                headPtr = s;
            }
        }
    }
    // assert(invariant());
}

int main()
{
    // make array
    SparseArray s;
    s.insert(2, "a");
    s.printNodes();
    s.insert(4, "b");
    s.printNodes();
   
}