usaco 2.1 sort3 2008.5.20

usaco 2.1 sort3 2008.5.20

{

ID:

PROG: sort3

LANG: PASCAL

}

program p_sort3;

constmaxn=1000;fin='sort3.in';fout='sort3.out';

type

arr1=array[1..maxn]of integer;

var

a,g:arr1;n,i,j,sum:longint;

p:array[1..3]of longint;

e:array[1..3,1..2]of longint;

f:array[1..maxn]of boolean;

f1,f2:text;

procedure init;

vari:longint;

begin

assign(f1,fin);reset(f1);

assign(f2,fout);rewrite(f2);

fillchar(p,sizeof(p),0);

fillchar(f,sizeof(f),true);

read(f1,n);

for i:=1 to n do begin read(f1,a[i]);inc(p[a[i]]);end;

e[1,1]:=1;e[1,2]:=p[1];

e[2,1]:=p[1]+1;e[2,2]:=p[1]+p[2];

e[3,1]:=p[1]+p[2]+1;e[3,2]:=n;

for i:=1 to p[1] do g[i]:=1;

for i:=e[2,1] to e[2,2] do g[i]:=2;

for i:=e[3,1] to e[3,2] do g[i]:=3;

sum:=0;

end;

procedure swap(var p1,p2:integer);

varx:integer;

begin x:=p1;p1:=p2;p2:=x;end;

procedure doit;

vari,ee:longint;

begin

for i:=1 to n do

if a[i]=g[i] then f[i]:=false

else

begin

inc(sum);j:=e[a[i],1]-1;

repeat inc(j);

until (((a[j]=g[i])and(f[j]))or(e[a[i],2]=j));

if g[i]=a[j] then

begin swap(a[i],a[j]);f[j]:=false;f[i]:=false;end

else

begin

ee:=yy-a[i]-g[i];j:=e[ee,1]-1;

repeat inc(j);

until (a[j]=g[i])and(f[j]);

swap(a[i],a[j]);

f[i]:=false;

end;

end;

end;

{-----------------------------}

begin

yy:=6;

init;

doit;

writeln(f2,sum);

close(f1);close(f2)

end.