Getting minimum number of MKMapRects from a MKPolygon - objective-c

Question

So I have a function that takes two MKMapRect's and the second intersects with the first one. So the function creates an MKPolygon that is the first rect without the intersecting parts:
-(void) polygons:(MKMapRect)fullRect exclude:(MKMapRect)excludeArea{
NSLog(#"Y is: %f height: %f",excludeArea.origin.y,excludeArea.size.height);
double top = excludeArea.origin.y - fullRect.origin.y;
double lft = excludeArea.origin.x - fullRect.origin.x;
double btm = (fullRect.origin.y + fullRect.size.height) - (excludeArea.origin.y + excludeArea.size.height);
double rgt = (fullRect.origin.x + fullRect.size.width) - (excludeArea.origin.x + excludeArea.size.width);
double ot = fullRect.origin.y, it = (ot + top);
double ol = fullRect.origin.x, il = (ol + lft);
double ob = (fullRect.origin.y + fullRect.size.height), ib = (ob - btm);
double or = (fullRect.origin.x + fullRect.size.width), ir = (or - rgt);
MKMapPoint points[11] = {{ol,it}, {ol,ot}, {or,ot}, {or,ob}, {ol,ob}, {ol,it}, {il,it}, {ir,it}, {ir,ib}, {il,ib}, {il,it}};
MKPolygon *polygon = [MKPolygon polygonWithPoints:points count:11];
}
And my question is now how do I get the minimum number of MKMapRects from this MKPolygon? I have done some googling as well as looking through the forum but havn't found anything.
EDIT:
So the goal is the following:
I have a MKMapRect rect1, then I have a list of rectangles, rectList, which is MKMapRects intersecting with rect1 and what I want to do is create a rectilinear MKPolygon of rect1, remove the surface of all MKMapRects in rectList from rect1 and then create the minimum number of MKMaprects from the created rectilinear MKPolygon.
Right now the problem is the following: I am able to create a polygon when removing one MKMapRect from rect1 but I dont know how to remove the following maprects from rect1 and I dont know how to extract the minimum set of MkMapRects from the polygon created.
Best regards
Peep

Answer 1

I'm not sure if this is what you're looking for or if I understand the question fully, but if all you need to know is the minimum number of rectangles in a polygon that's created by subtracting one rectangle from another you should be able to do it by checking the number of corner points in the second rectangle that are contained in the first rectangle. In pseudo code:
int minNumRects(MKRect r1, MKRect r2) {
int numPointsContained = 0;
for (Point p in r2) {
if (MKMapRectContainsPoint(r1, p)) {
numPointsContained++;
}
}
if (numPointsContained == 1) {
return 2;
} else if (numPointsContained == 2) {
return 3;
} else if (numPointsContained == 4) {
return 4;
} else {
return 0;
}
}
P.S. - This assumes that the rectangles are axis-aligned but as far as I know that's the case with MKRects