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c   pointer reference confusion
struct leaf
    {
        int data;
        leaf *l;
        leaf *r;
    };
    struct leaf *p;


void tree::findparent(int n,int &found,leaf *&parent)

leaf *&parent

void tree::findparent(int n,int &found,leaf *&parent)
{
    leaf *q;
    found=NO;
    parent=NULL;

    if(p==NULL)
        return;

    q=p;
    while(q!=NULL)
    {
        if(q->data==n)
        {
            found=YES;
            return;
        }
        if(q->data>n)
        {
            parent=q;
            q=q->l;
        }
        else
        {
            parent=q;
            q=q->r;
        }
    }
}

parent=q;

void passPointer(int *variable)
{
    *variable = (*variable)*2;
    variable = NULL; // THIS CHANGES THE LOCAL COPY NOT THE ACTUAL POINTER
}
void passPointerReference(int* &variable)
{
    *variable = (*variable)*3;
    variable = NULL; // THIS CHANGES THE ACTUAL POINTER!!!!
}
int main()
{
    int *pointer;
    pointer = new int;
    *pointer = 5;
    passPointer(pointer);
    cout << *pointer; // PRINTS 10
    passPointerReference(pointer);
    cout << *pointer; // GIVES ERROR BECAUSE VALUE OF pointer IS NOW 0.
    // The constant NULL is actually the number 0.
}