POJ 1830（位运算+双向DFS）
2012-09-01 11:31:48

[delphi
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.