var
  x,y,q:array[0..1101] of longint;
  n,i,k,top,l,t:longint;
  ans:real;

function cross(x1,y1,x2,y2,x3,y3:longint):longint;
begin
  cross:=(x2-x1)*(y3-y1)-(x3-x1)*(y2-y1);
end;

function dis(x1,y1,x2,y2:longint):real;
begin
  dis:=sqrt(sqr(x2-x1)+sqr(y2-y1));
end;

procedure sort;
var i,j:longint;
begin
  for i:=2 to n-1 do begin
    k:=i;
    for j:=i+1 to n do
    if (cross(x[1],y[1],x[j],y[j],x[k],y[k])>0)
    or (cross(x[1],y[1],x[j],y[j],x[k],y[k])=0)
    and (dis(x[1],y[1],x[j],y[j])<dis(x[1],y[1],x[k],y[k])) then k:=j;
    t:=x[i];x[i]:=x[k];x[k]:=t;
    t:=y[i];y[i]:=y[k];y[k]:=t;
  end;
end;

begin
  readln(n,l);x[0]:=1<<30;y[0]:=x[0];
  for i:=1 to n do begin
    readln(x[i],y[i]);
    if (y[i]<y[k]) or (y[i]=y[k]) and (x[i]<x[k]) then k:=i;
  end;
  t:=x[1];x[1]:=x[k];x[k]:=t;
  t:=y[1];y[1]:=y[k];y[k]:=t;
  sort;
  q[1]:=1;q[2]:=2;q[3]:=3;top:=3;
  for i:=4 to n do begin
    while (cross(x[q[top-1]],y[q[top-1]],x[i],y[i],x[q[top]],y[q[top]])>=0)
    do dec(top);
    inc(top);q[top]:=i;
  end;
  q[0]:=q[top];
  for i:=1 to top do ans:=ans+dis(x[q[i]],y[q[i]],x[q[i-1]],y[q[i-1]]);
  writeln(round(ans+2*pi*l));
end.



如果有两个点是同一个坐标会不会有问题？

• Re:求助，不管怎么调都过不了。 (1326) Yular 2011-03-18 23:23:27
  • Re:求助，不管怎么调都过不了。 (41) Yular 2011-03-18 23:24:28