"Нахождение выпуклой оболочки по заданным массивам точек на Pascal"

Код на Pascal
  
Program tochky;  
uses crt,graph;  
const kil=20;  
type TKoord=array [1..2] of integer;  
     TMaskoord=array [1..kil] of TKoord;  
var xy:TMaskoord;  
    per,n,i,j,k:integer;  
    driver,mode:integer;  
    max,maxb:real;  
    nmax1,nmax2,opukla:integer;  
    vec1,vec2:TKoord;  
procedure liniya(n1,n2:integer);  
begin  
if ((xy[n1,2]<0) and (xy[n2,2]<0)) then line(xy[n1,1]+320,-xy[n1,2]+240,xy[n2,1]+320,-xy[n2,2]+240) {obudvi vid'emni}  
                                   else begin  
if (xy[n1,2]<0) then line(xy[n1,1]+320,-xy[n1,2]+240,xy[n2,1]+320,240-xy[n2,2]) {persha vid'emna}  
                else if (xy[n2,2]<0) then line(xy[n1,1]+320,240-xy[n1,2],xy[n2,1]+320,-xy[n2,2]+240) {druga vid'emna}  
                                     else line(xy[n1,1]+320,240-xy[n1,2],xy[n2,1]+320,240-xy[n2,2]);  
                                        end  
end;  
   begin  
   {VVODUMO KOORDYNATY TOCHOK*************************************************}  
   textcolor(yellow);  
   per:=0;  
   i:=0;  
   repeat i:=i+1;  
          read(xy[i,1],xy[i,2]);  
          write('Exit - ? ');  
          readln(per);  
   until per=1;  
   n:=i; {v n kilkist tochok}  
   driver:=detect;  
   initgraph(driver,mode,'A:\');  
   {MALUEMO KOORDYNATNI OSI****************************************************}  
   setcolor(red);  
   line(320,0,320,480);  
   line(0,240,640,240);  
   line(320,0,310,10);  
   line(320,0,330,10);  
   line(310,10,330,10);  
   line(640,240,630,230);  
   line(640,240,630,250);  
   line(630,230,630,250);  
   setfillstyle(1,red);  
   floodfill(319,9,red);  
   floodfill(321,9,red);  
   floodfill(631,239,red);  
   floodfill(631,241,red);  
   outtextxy(335,10,'Y');  
   outtextxy(620,220,'X');  
   {VYZNACHAEMO MAXUMALNU VIDSTAN************************************************}  
   max:=0;  
   for i:=1 to n do for j:=1 to n do begin  
                                     maxb:=sqrt(sqr(xy[j,2]-xy[i,2])+sqr(xy[j,1]-xy[i,1]));  
                                     if maxb>max then begin  
                                                      max:=maxb;  
                                                      nmax1:=i;  
                                                      nmax2:=j;  
                                                      end;  
                                     end;  
   {mogna korustuvatysia zminnumu per,nmax1,nmax2:integer;  max,maxb:real}  
   {BUDUEMO OPUKLU OBOLONKU******************************************************}  
   {v n - kilkist tochok}  
   setcolor(lightblue);  
   setlinestyle(0,blue,1);  
   k:=nmax1;  
   for i:=1 to n do begin  
                    per:=0;  
                    if i=k then i:=i+1;  
                    if i=n+1 then break;  
                    vec1[1]:=xy[i,1]-xy[k,1];  
                    vec1[2]:=xy[i,2]-xy[k,2];  
                    for j:=1 to n do begin  
                                     vec2[1]:=xy[j,1]-xy[i,1];  
                                     vec2[2]:=xy[j,2]-xy[i,2];  
                                     max:=vec1[1]*vec2[2]-vec1[2]*vec2[1];  
                                     if max<0 then begin  
                                                   per:=1;  
                                                   break;  
                                                   end;{if max<0}  
                                     end;  {cykl po j}  
                                     if per=0 then begin  
                                     {z'ednuemo i i k tochku}  
                                                   liniya(i,k);  
                                                   k:=i;  
                                                   opukla:=i;  
                                                   i:=1;  
                                                   if opukla=nmax1 then break;  
                                                   end;{umova perevirku per=0}  
                          end;{cykl po i}  
   liniya(nmax1,opukla);    {ziednuemo ostanni tochky}  
   setcolor(white);  
   setlinestyle(3,white,1);  
   liniya(nmax1,nmax2); {maluemo naibilshu vidstan}  
   for i:=1 to n do if xy[i,2]<0 then putpixel(xy[i,1]+320,-xy[i,2]+240,yellow)  
                                 else putpixel(xy[i,1]+320,240-xy[i,2],yellow);  
   {POBUDUVALY TOCHKY,OPUKLU OBOLONKU I NAIBILSHU VIDSTAN****************************}  
   readln;  
   end.  
 
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