1185.pas

平时acm训练时ac的源代码

const eps = 0;
type real = extended;
type tpoint = record x, y: real; end;
var n, l: longint;
    mas: array [1..1000] of tpoint;
    an: array [1..1000] of real;
    ob: array [1..1000] of boolean;
    ans: array [1..1000] of longint;
    a, ang: real;
    i, j, k: longint;
    c, t: tpoint;
    v: array [1..3] of longint;
function getan(p: tpoint): real;
var x: real;
begin
     if p.x=0 then
     begin
          if p.y>0 then getan:=pi/2 else getan:=-pi/2;
          exit;
     end;
     x:=p.y/p.x;
     getan:=arctan(x);
end;
procedure fconvex;
var vp: real;
    v1, v2: tpoint;
begin
     v[1]:=2;
     v[2]:=3;
     v[3]:=4;
     i:=4;
     repeat
          v1.x:=mas[v[2]].x-mas[v[1]].x; v1.y:=mas[v[2]].y-mas[v
[1]].y;
          v2.x:=mas[v[3]].x-mas[v[2]].x; v2.y:=mas[v[3]].y-mas[v
[2]].y;
          vp:=v1.x*v2.y-v1.y*v2.x;
          if vp<eps then
          begin
               ob[v[2]]:=false;
               dec(k);
               v[2]:=v[1];
               dec(v[1]);
               while ob[v[1]]= false do dec(v[1]);
          end else
          begin
               v[1]:=v[2]; v[2]:=v[3]; i:=i mod n + 1; v[3]:=i;
          end;
     until i=2;
end;
begin
          read(n, l);
     c.x:=maxlongint;
     c.y:=maxlongint;
     fillchar(ob, sizeof(ob), false);
     for i:=1 to n do
     begin
          read(mas[i].x, mas[i].y);
          if (mas[i].x<c.x)or((mas[i].y<c.y)and(mas[i].x=c.x)) then 
c:=mas[i];
     end;
     for i:=1 to n do
     begin
          t.x:=mas[i].x-c.x;t.y:=mas[i].y-c.y;
          an[i]:=getan(t);
          j:=i;
          while (j>1)and(an[j]<an[j-1]) do
          begin
                a:=an[j];
                an[j]:=an[j-1];
                an[j-1]:=a;
                t:=mas[j];
                mas[j]:=mas[j-1];
                mas[j-1]:=t;
                dec(j);
          end;
     end;
     fillchar(ob, sizeof(ob), true);
     k:=n;
     if n>3 then
     fconvex;
     i:=1;
     j:=0;
     repeat
          while (i<n)and(not ob[i]) do inc(i);
          inc(j);
          ans[j]:=i;
          inc(i);
     until j=k;
     a:=0;
     for i:=1 to k-1 do
     begin
          ang:=sqr(mas[ans[i]].x-mas[ans[i+1]].x)+sqr(mas[ans[i]].y-
mas[ans[i+1]].y);
          ang:=sqrt(ang);
          a:=a+ang;
     end;
     ang:=sqrt(sqr(mas[ans[k]].x-mas[ans[1]].x)+sqr(mas[ans[k]].y-mas
[ans[1]].y));
     a:=a+ang;
     a:=a+2*pi*l;
     writeln(a:0:0);
end.