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class segment{
double x1,y1,x2,y2;
int name;
double nosac[3];
public:
segment():x1(0),y1(0),x2(0),y2(0),name(0){nosac[0]=nosac[1]=nosac[2]=0;}
segment(double X1,double Y1,double X2,double Y2);
void asign_name(int NAME){name=NAME;}
int return_name(){return name;}
int position(vector<double> point);
vector<double> left(){vector<double> P(2); P[0]=x1; P[1]=y1; return P;}
vector<double> right(){vector<double> K(2); K[0]=x2; K[1]=y2; return K;}
friend vector<double> intersect(segment a, segment b);
friend segment vrati_segment(vector<segment> S, int name);
friend bool kriterij_yY(segment a, segment b);
friend class kriterij_xXYy;
};
segment::segment(double X1,double Y1,double X2,double Y2):name(0){
if(X1<X2){x1=X1; y1=Y1; x2=X2; y2=Y2;}
else if(X1>X2){x1=X2; y1=Y2; x2=X1; y2=Y1;}
else{
if(Y1>Y2){x1=X1; y1=Y1; x2=X2; y2=Y2;}
else if (Y1<Y2){x1=X1; y1=Y2; x2=X2; y2=Y1;}
else throw "Segment cannot have length 0!\n";
}
nosac[0]=y1-y2;
nosac[1]=x2-x1;
nosac[2]=x1*y2-y1*x2;
}
int segment::position(vector<double> t){
if(x1==t[0] && y1==t[1])return 0;
else if(x2==t[0] && y2==t[1])return 2;
else if(min(x1,x2)<=t[0] && t[0]<=max(x1,x2) && min(y1,y2)<=t[1] &&
t[1]<=max(y1,y2) && (t[1]-y1)*(x2-x1)-(t[0]-x1)*(y2-y1)==0)return 1;
else return -1;
}
vector<double> intersect(segment a, segment b){
vector<double> N;
double p=b.nosac[0]*a.nosac[1]-a.nosac[0]*b.nosac[1];
if(!p){
N.push_back(0);
N.push_back(0);
N.push_back(0);
}
else{
N.push_back((b.nosac[1]*a.nosac[2]-a.nosac[1]*b.nosac[2])/p);
N.push_back((a.nosac[0]*b.nosac[2]-b.nosac[0]*a.nosac[2])/p);
if(min(a.x1,a.x2)<=N[0] && min(b.x1,b.x2)<=N[0] && max(a.x1,a.x2)>=N[0] &&
max(b.x1,b.x2)>=N[0] && min(a.y1,a.y2)<=N[1] && min(b.y1,b.y2)<=N[1] &&
max(a.y1,a.y2)>=N[1] && max(b.y1,b.y2)>=N[1])N.push_back(1);
else N.push_back(0);
}
return N;
}
segment vrati_segment(vector<segment> S, int NAME){
segment pom;
for(int i=0; i<S.size(); i++)if((S[i]).name==NAME)pom=S[i];
return pom;
}
class kriterij_xXYy{
public:
bool operator()(segment a, segment b)const
{return ((a.x1<b.x1 || (a.x1==b.x1 && a.y1>b.y1)) ||
((a.y1==b.y1 && a.x1==b.x1) && (a.x2!=b.x2 || a.y2!=b.y2)));}
};
class prioritet{
public:
bool operator()(vector<double> a, vector<double> b)const
{return a[0]>b[0] || (a[0]==b[0] && a[1]<b[1]);}
};
bool kriterij_yY(segment a, segment b){
return ((a.y1<b.y1 || (a.y1==b.y1 && a.x1>b.x1)) ||
((a.y1==b.y1 && a.x1==b.x1) && (a.x2!=b.x2 || a.y2!=b.y2)));
}
bool uQ (priority_queue <vector<double>,vector <vector<double> >,prioritet> Q, vector<double> point){
bool nalazise(false);
while(!Q.empty() && !nalazise){
vector<double> pom;
pom=Q.top();
Q.pop();
if(pom==point)nalazise=true;
}
return nalazise;
}
void napuniQ(vector<segment> &S, priority_queue<vector<double>,vector <vector<double> >,prioritet> &Q){
for(int i=0; i<S.size(); i++){
(S[i]).asign_name(i+1);
vector<double> rub;
rub=(S[i]).left();
if(!uQ(Q,rub))Q.push(rub);
rub=(S[i]).right();
if(!uQ(Q,rub))Q.push(rub);
}
}
vector< vector<double> > sweep_line(vector <segment> &S){
vector <vector<double> > P;
priority_queue <vector<double>,vector <vector<double> >,prioritet> Q;
napuniQ(S,Q);
set <segment,kriterij_xXYy> T;
set <segment,kriterij_xXYy> :: iterator Ti;
while(!Q.empty()){
vector <double> point;
point=Q.top();
Q.pop();
vector <segment> Lr,Tr,Dr;
for(int i=0; i<S.size(); i++){
int pt=(S[i]).position(point);
if(pt==0)Lr.push_back(S[i]);
else if(pt==2)Dr.push_back(S[i]);
else if(pt==1)Tr.push_back(S[i]);
}
sort(Lr.begin(),Lr.end(),kriterij_yY);
sort(Dr.begin(),Dr.end(),kriterij_yY);
sort(Tr.begin(),Tr.end(),kriterij_yY);
vector <segment> lUt,lUtUd,dUt;
merge(Lr.begin(),Lr.end(),Tr.begin(),Tr.end(),inserter(lUt,lUt.begin()),kriterij_yY);
merge(lUt.begin(),lUt.end(),Dr.begin(),Dr.end(),inserter(lUtUd,lUtUd.begin()),kriterij_yY);
merge(Dr.begin(),Dr.end(),Tr.begin(),Tr.end(),inserter(dUt,dUt.begin()),kriterij_yY);
if(lUtUd.size()>1){
P.push_back(point); // ---> intersection detected
}
vector <vector<int> > za_azuriranje;
vector <int> az;
int rbr_s, rbr_pr, rbr_slj;
for(int i=0; i<dUt.size(); i++){
Ti=T.lower_bound(dUt[i]);
segment pom;
if(Ti!=T.begin()){
Ti--;
pom=(*Ti);
rbr_pr=pom.return_name();
}
else rbr_pr=0;
Ti=T.upper_bound(dUt[i]);
if(Ti!=T.end()){
pom=(*Ti);
rbr_slj=pom.return_name();
}
else rbr_slj=0;
az.push_back(rbr_pr);
az.push_back(rbr_slj);
za_azuriranje.push_back(az);
}
vector <vector <int> > azuriraj;
for(int i=0; i<dUt.size(); i++){
try {
int ob;
ob=T.erase(dUt[i]);
if(ob && za_azuriranje[i][0] && za_azuriranje[i][1])
azuriraj.push_back(za_azuriranje[i]);
}
catch(...){}
}
for(int i=0; i<lUt.size(); i++){T.insert(lUt[i]);}
vector <double> pres;
if(lUt.empty()){
for(int i=0; i<azuriraj.size(); i++){
pres=intersect(vrati_segment(S,azuriraj[i][0]),vrati_segment(S,azuriraj[i][1]));
if(pres[2] && (pres[0]>point[0] || (pres[0]==point[0] && pres[1]<point[1]))){
pres.pop_back();
if(!(uQ(Q,pres)))Q.push(pres);
} //endIF
} //endFOR
} //endIF
else{
segment preth,sljedb;
for(int i=0; i<lUt.size(); i++){
if(T.lower_bound(lUt[i])!=T.begin()){
Ti=T.lower_bound(lUt[i]);
Ti--;
preth=(*Ti);
pres=intersect(preth,lUt[i]);
if(pres[2] && (pres[0]>point[0] || (pres[0]==point[0] && pres[1]<point[1]))){
pres.pop_back();
if(!(uQ(Q,pres)))Q.push(pres);
} //endIF
} //endIF
if(T.upper_bound(lUt[i])!=T.end()){
Ti=T.upper_bound(lUt[i]);
sljedb=(*Ti);
pres=intersect(lUt[i],sljedb);
if(pres[2] && (pres[0]>point[0] || (pres[0]==point[0] && pres[1]<point[1]))){
pres.pop_back();
if(!(uQ(Q,pres)))Q.push(pres);
} //endIF
} //endIF
} //endFOR
} //endELSE
} //endWHILE
return P;
}
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