POJ 1830(位运算+双向DFS)

此题也可用GE做,可是我不会矩阵乘法……

Program P1830;
const
   maxn=28;
   maxf=100007;
   none=-2139062144;
var
   ans,tt,n,i,j,s,t,mid:longint;
   b:array[1..29] of longint;
   h,num:array[0..maxf] of longint;

function hash(x:longint):longint;
var
   i,j:longint;
begin
   hash:=x mod maxf;
   while (num[hash]<>x) and (num[hash]<>none) do
   begin
      hash:=(hash+1) mod maxf;
   end;
   num[hash]:=x;
   exit(hash);
end;
procedure dfs(x,l:longint);
var
   i,j:longint;
begin
   if l=mid+1 then
   begin
      inc(h[hash(x)]);
      exit;
   end;
   for i:=l to mid do
      dfs(x xor b[i],i+1);
   dfs(x,mid+1);

end;
procedure find(x,l:longint);
var
   i,j:longint;
begin
   if l=n+1 then
   begin
      inc(ans,h[hash(x)]);
      exit;
   end;
   for i:=l to n do
      find(x xor b[i],i+1);
   find(x,n+1);

end;

begin
   read(tt);
   while (tt>0) do
   begin
      ans:=0;
      fillchar(b,sizeof(b),0);
      fillchar(num,sizeof(num),128);
      fillchar(h,sizeof(h),0);

      read(n);
      s:=0;
      for i:=1 to n do
      begin
         read(j);
         if j=1 then inc(s,1 shl (i-1));
      end;
      t:=0;
      for i:=1 to n do
      begin
         read(j);
         if j=1 then inc(t,1 shl (i-1));
      end;
      while (true) do
      begin
         read(i,j);
         if (i=0) and (j=0) then break;
         inc(b[i],1 shl (j-1));
      end;
      for i:=1 to n do inc(b[i],1 shl (i-1));
      mid:=n shr 1;
      dfs(s,1);
      find(t,mid+1);
      if ans=0 then writeln('Oh,it''s impossible~!!') else
      writeln(ans);
      dec(tt);
   end;
end.