FriedEgg,
I can't get result. My memory is broken.
I can't believe it can spend 5 seconds to find the answer. there is must be some special algorithm.
I am collapsed. 
data x(drop=r c);
length start $ 2;
retain c r;
if _n_ eq 1 then do;
input c r;
end;
else do;
do row=1 to r;
do col=1 to c;
start=cats(row,col);
input v @@;
if v ne 1 then output;
if v='2' then call symputx('start',cats(row,col));
else if v='3' then call symputx('end',cats(row,col));
end;
end;
end;
cards;
4 3
2 0 0 0
0 0 0 0
0 0 3 1
;
run;
data path(keep=start end);
if _n_ eq 1 then do;
if 0 then set x;
declare hash ha(dataset:'x');
ha.definekey('row','col');
ha.definedata('v');
ha.definedone();
end;
set x nobs=n end=last;
length end $ 2;
if start ne "&end" then do;
r=row-1;c=col;
if ha.find(key:r,key:c)=0 and v ne 2 then do;end=cats(r,c);output;end;
r=row+1;c=col;
if ha.find(key:r,key:c)=0 and v ne 2 then do;end=cats(r,c);output;end;
r=row; c=col-1;
if ha.find(key:r,key:c)=0 and v ne 2 then do;end=cats(r,c);output;end;
r=row; c=col+1;
if ha.find(key:r,key:c)=0 and v ne 2 then do;end=cats(r,c);output;end;
end;
if last then call symputx('n',n-1);
run;
data _null_;
if 0 then set path;
declare hash ha(hashexp:10,dataset:'path',multidata:'Y');
declare hiter hi('ha');
ha.definekey('start');
ha.definedata('start','end');
ha.definedone();
length path _path $ 200;
declare hash _ha(hashexp:10,ordered:'Y');
declare hiter _hi('_ha');
_ha.definekey('count');
_ha.definedata('count','path');
_ha.definedone();
set path(where=(start="&start")) end=last;
x=0;x+1;count=x;path=catx(' ',start,end);_ha.add();
rc=_hi.first();
do while(rc=0);
_path=path;index=scan(_path,-1); _count=count;
do while(hi.next()=0);
if index=start then do;
if not find(path,end) then do;
if end ne "&end" then do;
x+1;count=x;path=catx(' ',path,end);_ha.add();path=_path;
end;
else if countw(path)=&n then n_path+1;
end;
end;
end;
rc=_hi.next();
rx=_ha.remove(key:_count);
end;
if last then putlog "How many path: " n_path ;
run;
Ksharp
