不要开标记数组，因为一个点可能由多个方向到达
跟我犯同样错误的同志们注意了……
附ac代码：
var
  d:array[1..4,1..2] of longint=((0,1),(1,0),(0,-1),(-1,0));
  a:array[0..30,0..30] of integer;
  ans,tot,n,m,sx,sy:longint;

procedure init;
var
  i,j:longint;
begin
  for i:=1 to n do
  begin
    for j:=1 to m do
	begin
	  read(a[i,j]);
	  if a[i,j]=2 then
	  begin
	    sx:=i;sy:=j;
	  end;
	end;
    readln;
  end;
end;

procedure dfs(x,y:longint);
var
  i,xx,yy,temp1,temp2:longint;
begin
  if tot+1>=ans then exit;
  for i:=1 to 4 do
  begin
    xx:=x+d[i,1];
	yy:=y+d[i,2];
	if (a[xx,yy]=1)or(xx<=0)or(yy<=0)or(xx>n)or(yy>m) then continue;
    xx:=x;yy:=y;
    while(a[xx,yy]<>1)and(xx>0)and(yy>0)and(xx<=n)and(yy<=m)do
	begin
	  xx:=xx+d[i,1];
	  yy:=yy+d[i,2];
	  if a[xx,yy]=3 then
	  begin
	    if (tot+1<ans) then ans:=tot+1;
		exit;
	  end;
	end;
	if (a[xx,yy]=1)then
	begin
	  temp1:=xx-d[i,1]; temp2:=yy-d[i,2];
	  begin
		inc(tot);
		a[xx,yy]:=0;
		dfs(temp1,temp2);
		dec(tot);
		a[xx,yy]:=1;
	  end;
	end;
  end;
end;

begin
  readln(m,n);
  while(m<>0)and(n<>0)do
  begin
    fillchar(a,sizeof(a),0);
    init;
	ans:=11;
	tot:=0;
	dfs(sx,sy);
	if ans<>11 then
	  writeln(ans)
	else writeln(-1);
	readln(m,n)
  end;
end.