USACO 6.4.3 Wisconsin Squares dfs

直接dfs就好了，并不用什么优化，因为时限是5s……

代码：

{
ID: ymwbegi1
PROG: wissqu
LANG: PASCAL
}

const
  dl:array[1..5] of longint=(3,3,3,4,3);
  ch:array[1..1] of longint=(4);

var
  i,j,ans:longint;
  flag:boolean;
  f,ansf:array[1..16,1..3] of longint;
  s:array[1..5,1..4,1..4] of longint;
  v:array[1..4,1..4] of boolean;
  a:array[1..4,1..4] of longint;
  d:array[1..5] of longint;
  c:char;

function min(x,y:longint):longint;
begin
  if x<y then exit(x)
         else exit(y);
end;

function max(x,y:longint):longint;
begin
  if x>y then exit(x)
         else exit(y);
end;

procedure work(z,x,y,w:longint);
var
  i,j:longint;
begin
  for i:=max(x-1,1) to min(x+1,4) do
    for j:=max(y-1,1) to min(y+1,4) do
      inc(s[z,i,j],w);
end;

procedure print;
var
  i:longint;
begin
  for i:=1 to 16 do
    writeln(chr(ansf[i,1]+ord('A')-1),' ',ansf[i,2],' ',ansf[i,3]);
  writeln(ans);
end;

procedure dfs(x:longint);
var
  i,j,k:longint;
begin
  if x=17 then
  begin
    inc(ans);
    if flag then
    begin
      ansf:=f;
      flag:=false;
    end;
    exit;
  end;
  if x<2
    then begin
           for i:=1 to 4 do
             for j:=1 to 4 do
               if (s[ch[x],i,j]=0)and(v[i,j]) then
               begin
                 f[x,1]:=ch[x];
                 f[x,2]:=i;
                 f[x,3]:=j;
                 v[i,j]:=false;
                 work(a[i,j],i,j,-1);
                 work(ch[x],i,j,1);
                 inc(d[ch[x]]);
                 dfs(x+1);
                 v[i,j]:=true;
                 work(ch[x],i,j,-1);
                 work(a[i,j],i,j,1);
                 dec(d[ch[x]]);
               end;
         end
    else for k:=1 to 5 do
           if d[k]<dl[k] then
             for i:=1 to 4 do
               for j:=1 to 4 do
                 if (s[k,i,j]=0)and(v[i,j]) then
                 begin
                   f[x,1]:=k;
                   f[x,2]:=i;
                   f[x,3]:=j;
                   work(k,i,j,1);
                   work(a[i,j],i,j,-1);
                   inc(d[k]);
                   v[i,j]:=false;
                   dfs(x+1);
                   v[i,j]:=true;
                   work(k,i,j,-1);
                   work(a[i,j],i,j,1);
                   dec(d[k]);
                 end;
end;

begin
  assign(input,'wissqu.in');
  assign(output,'wissqu.out');
  reset(input);
  rewrite(output);
  for i:=1 to 4 do
    for j:=1 to 4 do
    begin
      if j<4
        then read(c)
        else readln(c);
      a[i,j]:=ord(c)-ord('A')+1;
      work(a[i,j],i,j,1);
    end;
  flag:=true;
  fillchar(v,sizeof(v),true);
  dfs(1);
  print;
  close(input);
  close(output);
end.