Question

Say I have the following:

bool signal(QtreeNode * & orig, QtreeNode * & n, int tolerance) {

    bool signal1= false, signal2= false, signal3= false, signal4= false;
    if(n->isLeaf()){
        if(totalDiff>tolerance) //suppose these were defined
            return true;
        else return false;
    }
    signal1=signal(orig, n->neChild, tolerance); 
    signal2=signal(orig, n->nwChild, tolerance);
    signal3=signal(orig, n->swChild, tolerance);
    signal4=signal(orig, n->seChild, tolerance);

    if(signal1 || signal2 || signal3 || signal4)
        return true;
    else return false;
}

And say I call that method from some wrapper method like this:

signal1=signal(orig, n, tolerance);
    if(signal1)
        //do something

So what I’m doing here is traversing an entire quad-tree looking for just one case where I get true. All I need for this function to do is to return true in one case where totalDiff is greater than tolerance. I’m afraid that what I have isn’t doing what I hoped it would do. Looking at function, does it seem like, when I set signal1 in my wrapper method, that I will get true back if it finds just 1 case of that condition? Or am I doing it wrong?

Answer 1

You’ll hit every leaf in your quadtree this way. Instead you want to break as soon as you’ve found it. To do that you need to change

signal1=signal(orig, n->neChild, tolerance); 
signal2=signal(orig, n->nwChild, tolerance);
signal3=signal(orig, n->swChild, tolerance);
signal4=signal(orig, n->seChild, tolerance);

if(signal1 || signal2 || signal3 || signal4)
    return true;
else return false;

to

return signal(orig, n->neChild, tolerance) || 
       signal(orig, n->nwChild, tolerance) ||
       signal(orig, n->swChild, tolerance) ||
       signal(orig, n->seChild, tolerance);