Триангуляция невыпуклого многоугольника

unit Trianguliation;
 
interface
 
uses
    Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
    Dialogs, ExtCtrls;
 
type
    TForm1 = class(TForm)
        PaintBox1: TPaintBox;
        procedure PaintBox1Click(Sender: TObject);
        function V(p1, p2, p3: TPoint): Integer;
    end;
 
var
    Form1: TForm1;
    Brush: TBrush;
    a: Array [0..11] of TPoint; 
    used: Array [0..30] of Integer; 
    b: Array [0..30] of Array [0..2] of Tpoint;
    i, j, k, m, n, cnt, ok: Integer;
 
implementation
 
{$R *.dfm}
 
procedure TForm1.PaintBox1Click(Sender: TObject);
begin
    with PaintBox1.Canvas do begin
 
        a[0] := Point(100, 400); 
        a[1] := Point(100, 100);
        a[2] := Point(200, 600);
        a[3] := Point(300, 400);
        a[4] := Point(200, 300);
        a[5] := Point(500, 300);
        a[6] := Point(300, 500);
        a[7] := Point(600, 500);
        a[8] := Point(600, 0);
        a[9] := Point(400, 100);
        a[10] := Point(0, 0);
 
        Polygon(a); 
 
        for i := 0 to 30 do     
            used[i] := 0;
        cnt := 11; n := 0;
        i := 0; j := 1; k := 2;
 
        while(cnt > 3) do begin    
            cnt := 0; ok := 0;
            if(V(a[i], a[j], a[k]) < 0) then begin   
                ok := 1;
                for m := 0 to 10 do begin           
                    if(used[m] = 0) and
                    (((V(a[i], a[j], a[m]) > 0) and (V(a[j], a[k], a[m]) > 0) and (V(a[k], a[i], a[m]) > 0)) or
                    ((V(a[i], a[j], a[m]) < 0) and (V(a[j], a[k], a[m]) < 0) and (V(a[k], a[i], a[m]) < 0))) then
                        ok := 0;
                end;
            end;
 
            if(ok = 1) then begin
 
                b[n][0] := a[i];
                b[n][1] := a[j];
                b[n][2] := a[k];
                n := n + 1;
                used[j] := 1;
                j := k;
 
                                for m := k + 1 to 21 do
                    if(used[m mod 11] = 0) then begin
                        k := m mod 11;
                        break;
                    end;
 
                for m := 0 to 10 do
                  if(used[m] = 0) then
                      cnt := cnt + 1;
            end
            else begin
                for m := i + 1 to 21 do
                    if(used[m mod 11] = 0) then begin
                        i := m mod 11;
                        break;
                    end;
                for m := j + 1 to 21 do
                    if(used[m mod 11] = 0) then begin
                        j := m mod 11;
                        break;
                    end;
                for m := k + 1 to 21 do
                  if(used[m mod 11] = 0) then begin
                    k := m mod 11;
                    break;
                  end;
            end;
            if(cnt = 0) then cnt := 4;
        end;
 
        i := 0;
 
        for m := 0 to 10 do
            if(used[m] = 0) then begin
            b[n][i] := a[m];
            i := i + 1;
          end;
        for i := 0 to n do begin   
            Brush.Color := RGB(Random(50000) mod 256, Random(50000) mod 256, Random(50000) mod 256);
            Polygon(b[i]);
        end;
    end;
end;
 
function TForm1.V(p1, p2, p3: TPoint): Integer;
begin
    Result := (p2.x - p1.x) * (p3.y - p1.y) - (p2.y - p1.y) * (p3.x - p1.x);
end;
 
end.