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## Discussion of Problem 1331. Vladislava

How to avoid TLE?(-)
Posted by Maigo Akisame (maigoakisame@yahoo.com.cn) 20 Oct 2004 15:09
Use double instead of extended (-)
Posted by Dmitry 'Diman_YES' Kovalioff 20 Oct 2004 16:46
But I use real everywhere and do as much pre-calculation as possible. It's still TLE on test #4.
Posted by Maigo Akisame (maigoakisame@yahoo.com.cn) 21 Oct 2004 04:45
program ural1331;
const
maxm=5000;
zero=1e-6;
var
w,l,x,y,z:array[1..maxm]of real;
n,m,i,j:word;
r,ww,ll,xx,yy,zz,ans:real;
procedure calcoord(var w,l,x,y,z:real);
begin
w:=w*pi/180;
l:=l*pi/180;
x:=cos(w)*cos(l);
y:=cos(w)*sin(l);
z:=sin(w);
end;
function min(a,b:real):real;
begin
if a<b then min:=a else min:=b;
end;
function arcsin(s:real):real;
begin
if s>1-zero then
arcsin:=pi/2
else
arcsin:=arctan(s/sqrt(1-s*s));
end;
begin
for i:=1 to m do begin
calcoord(w[i],l[i],x[i],y[i],z[i]);
end;

for i:=1 to n do begin
calcoord(ww,ll,xx,yy,zz);
ans:=1e38;
for j:=1 to m do
ans:=min(ans,sqr(xx-x[j])+sqr(yy-y[j])+sqr(zz-z[j]));
writeln(arcsin(sqrt(ans)/2)*2*r:0:2);
end;
end.
There are a lot of calculations in your program - optimize it (-)
Posted by Dmitry 'Diman_YES' Kovalioff 21 Oct 2004 22:25
Calling "min" function slows your program (-)
Posted by Michael Rybak (accepted@ukr.net) 25 Oct 2004 23:02

Edited by author 26.10.2004 00:27
Thanks. I use dot product this time and deleted the min/max function. Ac in 0.671s.
Posted by Maigo Akisame (maigoakisame@yahoo.com.cn) 26 Oct 2004 04:39
Use octtree structure (+)
Posted by Korduban [Kiev] 7 Feb 2005 23:01
subj. My program get AC in 0.302 (without optimizations). I think it's possible to reduce time to 0.150 sec

http://acm.timus.ru/status.aspx?space=1&pos=737505

Edited by author 07.02.2005 23:03
Strange! My brute force got AC in 0.39. And what is it "octtree structure" (-)
Posted by Ariel 8 Feb 2005 00:11
Could you mail your AC code to dkorduban [at] ukr.net? (-)
Posted by Korduban [Kiev] 8 Feb 2005 15:56
Accepted in 0.171 (+)
Posted by Korduban [Kiev] 9 Feb 2005 17:41
Re: Accepted in 0.171 (+)
Posted by svr 20 Nov 2006 14:32
Middle time of speed can be taken by using
simple qsort of points by key=max(y[i],i=1,..3)
and then log-time search of pozition of point x[k]
under consideration in sorted array with
cutting off parts of array y which
far enough from the pozition.