poj 3322 Bloxorz I
基础的BFS题目，但是发现自己好久没有做过搜索题了，这道题做的很不爽，尤其是方向常量的处理，完全抄袭了他人的。
代码：
const
nx:array[0..2,1..4] of integer=((1,-2,0,0),(1,-1,0,0),(0,0,-1,2));
ny:array[0..2,1..4] of integer=((0,0,1,-2),(0,0,-1,2),(1,-1,0,0));
ns:array[0..2,1..4] of integer=((2,2,1,1),(1,1,0,0),(2,2,0,0));
type
ji=record
x,y,s,w:longint;
end;
var
q:array[0..2000000] of ji;
a:array[0..511,0..511] of char;
v:array[0..511,0..511,0..2] of boolean;
n,m,s,t,head,tail,now,w,x,y,i,j,k:longint;
nt:ji;
vv:boolean;
begin
readln(n,m);
while n<>0 do
begin
for i:=0 to n+1 do
for j:=0 to m+1 do
a[i,j]:='#';
vv:=false;
t:=0;
fillchar(v,sizeof(v),0);
for i:=1 to n do
begin
for j:=1 to m do
begin
read(a[i,j]);
if a[i,j]='O' then
begin
nt.x:=i;
nt.y:=j;
nt.s:=0;
end else
if a[i,j]='X' then
begin
if t=0 then
begin
q[1].x:=i;
q[1].y:=j;
q[1].s:=0;
x:=i;
y:=j;
t:=1;
v[x,y,0]:=true;
now:=1;
end else
begin
v[x,y,0]:=false;
if i=x then now:=1
else now:=2;
v[x,y,now]:=true;
q[1].s:=now;
end;
end;
end;
readln;
end;
head:=1; tail:=1; q[1].w:=0;
while head<=tail do
begin
x:=q[head].x; y:=q[head].y; now:=q[head].s; w:=q[head].w+1;
for i:=1 to 4 do
begin
s:=q[head].x+nx[now,i];
t:=q[head].y+ny[now,i];
k:=ns[now,i];
if (s<1)or(t<1)or(s>n)or(t>m) then continue;
if a[s,t]='#' then continue;
if (k=0)and(a[s,t]='E') then continue;
if (k=1)and(a[s,t+1]='#') then continue;
if (k=2)and(a[s+1,t]='#') then continue;
if v[s,t,k] then continue;
v[s,t,k]:=true;
inc(tail);
q[tail].x:=s; q[tail].y:=t; q[tail].s:=k; q[tail].w:=w;
if (q[tail].x=nt.x)and(q[tail].y=nt.y)and(k=0) then
begin
writeln(w);
vv:=true;
break;
end;
end;
if vv then break;
inc(head);
end;
if not vv then writeln('Impossible');
readln(n,m);
end;
end.