USACO 6.5.4 The Clocks bfs

朴素bfs就好了。用四进制记录状态然后判重。

代码：

{
ID: ymwbegi1
PROG: clocks
LANG: PASCAL
} 

var
  w:array[1..9] of longint;
  state:array[1..300000,1..9] of longint;
  v:array[0..300000] of boolean;
  flag:boolean;
  i,x:longint;
  f,d:array[1..300000] of longint;
  s:array[0..9] of longint;
  a:array[1..9,0..5] of longint;

procedure print(x:longint);
begin
  if f[x]=0 then exit;
  print(f[x]);
  if flag
    then flag:=false
    else write(' ');
  write(d[x]);
end;

procedure bfs;
var
  head,tail,i,j,tot:longint;
begin
  head:=0;
  tail:=1;
  repeat
    inc(head);
    for i:=1 to 9 do
    begin
      w:=state[head];
      for j:=1 to a[i,0] do
        w[a[i,j]]:=(w[a[i,j]]+1) mod 4;
      tot:=0;
      for j:=1 to 9 do
        tot:=tot+s[j-1]*w[j];
      if v[tot] then
      begin
        inc(tail);
        state[tail]:=w;
        f[tail]:=head;
        d[tail]:=i;
        v[tot]:=false;
        if tot=0 then
        begin
          print(tail);
          writeln;
          exit;
        end;
      end;
    end;
  until head>=tail;
end;

procedure work;
begin
  a[1,0]:=4; a[1,1]:=1; a[1,2]:=2; a[1,3]:=4; a[1,4]:=5;
  a[2,0]:=3; a[2,1]:=1; a[2,2]:=2; a[2,3]:=3;
  a[3,0]:=4; a[3,1]:=2; a[3,2]:=3; a[3,3]:=5; a[3,4]:=6;
  a[4,0]:=3; a[4,1]:=1; a[4,2]:=4; a[4,3]:=7;
  a[5,0]:=5; a[5,1]:=2; a[5,2]:=4; a[5,3]:=5; a[5,4]:=6; a[5,5]:=8;
  a[6,0]:=3; a[6,1]:=3; a[6,2]:=6; a[6,3]:=9;
  a[7,0]:=4; a[7,1]:=4; a[7,2]:=5; a[7,3]:=7; a[7,4]:=8;
  a[8,0]:=3; a[8,1]:=7; a[8,2]:=8; a[8,3]:=9;
  a[9,0]:=4; a[9,1]:=5; a[9,2]:=6; a[9,3]:=8; a[9,4]:=9;
end;

begin
  assign(input,'clocks.in');
  assign(output,'clocks.out');
  reset(input);
  rewrite(output);
  work;
  flag:=true;
  for i:=1 to 9 do
  begin
    read(x);
    case x of
      3:state[1,i]:=1;
      6:state[1,i]:=2;
      9:state[1,i]:=3;
      12:state[1,i]:=0;
    end;
  end;
  s[0]:=1;
  for i:=1 to 9 do
    s[i]:=s[i-1]*4;
  fillchar(v,sizeof(v),true);
  bfs;
  close(input);
  close(output);
end.