コード例 #1
0
void convex_hull(polygon in, polygon& hull){
	hull.clear();
	
	if(in.size() < 3){ hull = in; return; }
	
	int pos = 0;
	for(int i = 1; i < in.size(); i++) if(in[i] < in[pos]) pos = i;
	swap(in[0], in[pos]);
	refer = in[0];
	
	sort(in.begin() + 1, in.end(), cmp_angle);
	in.resize(unique(in.begin(), in.end()) - in.begin());
	
	hull.push_back(in[0]); hull.push_back(in[1]);
	
	in.push_back(in[0]); //isto evita pontos colineares no final do poligono
	for(int i = 2; i < in.size(); ){
		if(hull.size() > 2 && side_sign(hull[hull.size() - 2], hull[hull.size() - 1], in[i]) <= 0){
			hull.pop_back();
		}
		else hull.push_back(in[i++]);
	}
	//tira a duplicata
	hull.pop_back();
}
コード例 #2
0
//testa se o ponto esta dentro de um poligono (nao necessariamente convexo)
bool inside_poly(pt p, polygon poly){
	poly.push_back(poly[0]);
	
	for(int i = 0; i < poly.size()-1; i++)
		if(point_and_seg(poly[i], poly[i+1], p)) return true; //na borda
	
	for(int i = 0; i < poly.size()-1; i++) poly[i] = poly[i] - p;
	p = pt(0, 0);
	
	double theta, y;
	
	while(true){
		theta = (double)rand()/10000.0;
		
		bool inter = false;
		//evita que um ponto fique no eixo x
		for(int i = 0; i < poly.size()-1; i++){
			poly[i] = rotate(poly[i], theta);
			if( !cmp(poly[i].x) ) inter = true;
		}
		
		if( !inter ){
			poly[poly.size()-1] = poly[0];
			//testa as possiveis intersecoes
			for(int i = 0; i < poly.size()-1; i++){
				if( cmp( poly[i].x * poly[i+1].x ) < 0 ){
					y = poly[i+1].y - poly[i+1].x * (poly[i].y - poly[i+1].y) / (poly[i].x - poly[i+1].x);
					if( cmp(y) > 0 ) inter = !inter; //se interecao valida
				}
			}
			return inter; //testa a paridade da semi-reta vertical partindo de p
		}
	}
	return true;
}
コード例 #3
0
// Returns a list of points on the convex hull in counter-clockwise order.
// NOTE: the last point in the returned list is the same as the first one.
void convex_hull_2(polygon P, polygon& hull) {
	hull.clear();
	
	// Sort points lexicographically
	sort(P.begin(), P.end());
	P.resize(unique(P.begin(), P.end()) - P.begin());
	
	// Build lower hull
	for (int i = 0; i < P.size(); i ++) {
		while (hull.size() >= 2 && side_sign(hull[hull.size() - 2], hull[hull.size() - 1], P[i]) <= 0)
			hull.pop_back();
		hull.push_back(P[i]);
	};
 
	// Build upper hull
	for (int i = P.size()-2, t = hull.size() + 1; i >= 0; i --) {
		while (hull.size() >= t && side_sign(hull[hull.size()-2], hull[hull.size()-1], P[i]) <= 0)
			hull.pop_back();
		hull.push_back(P[i]);
	};
}
コード例 #4
0
ファイル: program.cpp プロジェクト: metaphysis/Code
void rotatingCalipers(polygon pg)
{
    pg.push_back(pg.front());
    for (int i = 0, j = 1, n = pg.size() - 1; i < n; i++)
    {
        while (cross(pg[i + 1] - pg[i], pg[j + 1] - pg[j]) > 0)
            j = (j + 1) % n;
        double dist1 = pg[i].distTo(pg[j - 1]);
        double dist2 = pg[i].distTo(pg[j]);
        double dist3 = pg[i].distTo(pg[j + 1]);
        int r1 = j + 1, r2 = j + 2;
        cout << (j - 1) << '=' << dist1 << ' ' << j << '=' << dist2 << ' ' << (j + 1) << '=' << dist3 << '\n';
        if (r1 >= n) r1 = 1;
        if (r2 >= n) r2 = 1;
        if (dist2 > dist3) cout << r1 << '\n';
        else if (dist3 > dist2) cout << r2 << '\n';
        else cout << min(r1, r2) << '\n';
    }
}