Sudoku/REXX

From Rosetta Code
Sudoku/REXX is part of Sudoku. You may find other members of Sudoku at Category:Sudoku.

REXX[edit]

REXX version 1[edit]

This is the   $SUDOKU.REX   (REXX) program and is used to solve the Rosetta Code task of "sudoku".


This REXX program was originally written to assist in sudoku puzzle solving (by giving strong hints), and not to solve the puzzle outright.

The REXX program was written to give increasing better hints and also show the possibilities (of what is possible solution for any cell),
and to partially solve the puzzle using distinct strategies (separately or in combination).   One option is to solve the puzzle.

The help for the   $SUDOKU   REXX program is included here   ───►   $SUDOKU.HEL.

The   $SUDOKU.REX   REXX program makes use of   $ERR.REX   REXX program which is used to display error messages (via   $T.REX).

The   $ERR.REX   REXX program is included here   ───►   $ERR.REX.

The   $SUDOKU.REX   REXX program makes use of   $T.REX   REXX program which is used to display text messages.

The   $T.REX   REXX program is included here   ───►   $T.REX.

Some older REXXes don't have a   changestr   BIF, so one is included here   ───►   CHANGESTR.REX.

REXX programs   not   included are   $H   which shows/displays help and other documentation.

/*REXX program displays, can give hints, and/or solve a sudoku puzzle.  */
trace off
parse arg !
if !all(arg()) then exit
if !cms then address ''
signal on halt
signal on noValue
signal on syntax
 
ops=! /*remove extraneous blanks.*/
numeric digits 20
combos=1
@.=' ' /*initialize grid to blanks*/
!.= /*nullify valid empty# list*/
@abc='abcdefghijklmnopqrstuvwxyz'
@[email protected]
upper @abcU
colors=!cms | !pcrexx | !r4 | !roo /*Are colors supported ? */
clear=1 /*option: clear the screen.*/
highLight=0 /*option: highlight singles*/
pruneall=0 /*option: prune all. */
prunemats=0 /*option: prune matches. */
prunesing=0 /*option: prune singles. */
pruneexcl=0 /*option: prune exclusives.*/
pruneline=0 /*option: prune lines. */
pruneonly=0 /*option: prune onlys. */
simple=0 /*option: show simple boxes*/
showoneline=0 /*option: show grid as1line*/
showgrid=1 /*option: show the grid. */
showinfo=1 /*option: show informatiion*/
showposs=0 /*option: show possible val*/
showcomb=0 /*option: show combinations*/
showrow= /*option: SHOWPOSS for rowN*/
showcol= /*option: SHOWPOSS for colN*/
showbox= /*option: SHOWPOSS for boxN*/
showcell= /*option: SHOWPOSS cellRC */
short=0
solve=0 /*option: solve the puzzle.*/
sod=lower(translate(!fn,,'$')) /*name of the puzzle. */
tellinvalid=1 /*tell err msg if invalid X*/
tops= /*option: used for $T opts.*/
 
gridindents=3 /*# spaces grid is indented*/
gridindent=left('',gridindents) /*spaces indented for grid.*/
gridwidth=7 /*grid cell interior width.*/
gridbar='b3'x /*bar for the grid (cells).*/
gridlt='da'x /*grid cell left top. */
gridrt='bf'x /*grid cell right top. */
gridlb='c0'x /*grid cell left bottom. */
gridrb='d9'x /*grid cell right bottom. */
gridline='c4'x /*grid cell line (hyphen). */
gridlin=copies(gridline,gridwidth) /*grid cell total line. */
gridemp=left('',gridwidth) /*grid cell empty (spaces).*/
griddj='c2'x /*grid cell down junction.*/
griduj='c1'x /*grid cell up junction.*/
gridlj='c3'x /*grid cell left junction.*/
gridrj='b4'x /*grid cell right junction.*/
gridcross='c5'x /*grid cell cross junction.*/
 
do while ops\=='' /*parse any and all options*/
parse var ops _1 2 1 _ . 1 _o ops
upper _
 
select
when _==',' then nop
when _1=='.' & pos("=",_)\==0 then tops=tops _o
 
when abb('PUZzle') then /*do PUZZ (whole) placement*/
do
puzz=na()
if length(puzz)>81 then call er 30,puzz 'PUZZLE 1───►81'
 
do j=1 for length(puzz)
q=substr(puzz,j,1)
if q=='.' then iterate
call vern q,'PUZZLE_digit'
c=j//9
if c==0 then c=9
r=(j-1)%9 + 1
@.r.c=q
end /*j*/
end
 
when _=='CELL' then /*do CELL (grid) placement.*/
do
rc=nai()
if length(rc)\==2 then call er 30,y 'CELL'rc 2
y=na()
if length(y)>1 then call er 30,y 'CELL'rc 1
r=left(rc,1)
c=right(rc,1)
call vern r,'CELLrow'
call vern c,'CELLcolumn'
call vern y,'CELLdigit'
@.r.c=y
end
 
when abb('COLumn') then /*do ROW (grid) placement. */
do
n=nai()
y=na()
call vern n,'column'
ly=length(y)
if ly>9 then call er 30,y 'column'n '1───>9'
 
do j=1 for ly
x=substr(y,j,1)
if x=='' | x=="_" | x=='*' | x=="." then iterate
if \isInt(x) then call er 92,x 'cell_for_column'n
@.j.n=x
end /*j*/
end
 
when abb('ROW') then /*do ROW (grid) placement. */
do
n=nai()
y=na()
call vern n,'row'
ly=length(y)
if ly>9 then call er 30,y 'row'n '1───>9'
 
do j=1 for ly
x=substr(y,j,1)
if x=='' | x=="_" | x=='*' | x=="." then iterate
if \isInt(x) then call er 92,x 'cell_for_row_'n
@.n.j=x
end /*j*/
end
 
when abbn('CLearscreen') then clear=no()
when abbn('HIGHLightsingles') then highLight=no()
when abbn('PRUNEALL') then pruneall=no()
when abbn('PRUNEONLYs') then pruneonly=no()
when abbn('PRUNEEXclusives') then pruneexcl=no()
when abbn('PRUNELINEs') then pruneline=no()
when abbn('PRUNEMATches') then prunemats=no()
when abbn('PRUNESINGles') then prunesing=no()
when abbn('SIMPle') then simple=no()
when abb('SHOWBOXes')|,
abb('SHOWBOXs') then showbox=nai()
when abb('SHOWCELLs') then showcell=translate(na(),,',')
when abb('SHOWCOLs') then showcol=nai()
when abbn('SHOWCOMBinations') then showcomb=no()
when abbn('SHOWGrid') then showgrid=no()
when abbn('SHOWINFOrmation') then showinfo=no()
when abbn('SHOWONELINE') then showoneline=no()
when abbn('SHOWPOSSibles') then showposs=no()
when abb('SHOWROWs') then showrow=nai()
when abbn('SHortgrid') then short=no()
when abbn('SOLvepuzzle') then solve=no()
 
otherwise call er 55,_o
end /*select*/
end /*while ops¬==''*/
 
if solve then pruneall=1 /*if solving, use PRUNEALL.*/
 
if pruneall then do /*if pruneAll, set ON other*/
pruneexcl=1
pruneonly=1
pruneline=1
prunemats=1
prunesing=1
end
 
aprune = , /*is there a PRUNExxx on ? */
pruneexcl |,
pruneonly |,
pruneline |,
prunemats |,
prunesing
 
if highLight then do /*HIGHLIGHTSINGLES opt on? */
hLl='-'
hLr='-'
 
if colors then do
hLl='('
hLr=')'
tops='.H=yell' tops
end
end
 
tops=space(tops)
box.=
 
do j=1 for 9 /*build the box bounds. */
rr=(((j*3)%10)+1)*3-2 /*compute row lower bound. */
cc=(((j-1)//3)+1)*3-2 /*compute col lower bound. */
boxr.j=rr
boxc.j=cc
 
do r=rr to rr+2 /*build boxes with cell #s.*/
do c=cc to cc+2
rc=r || c
box.j=box.j rc
box.rc=j
end /*c*/
end /*r*/
 
box.j=strip(box.j)
end /*j*/
 
rowlb.=10 /*row R, low box number=b.*/
collb.=10 /*col R, low box number=b.*/
boxlr.=10 /*box B, low row number=r.*/
boxlc.=10 /*box B, low col number=c.*/
 
do r=1 for 9
do c=1 for 9
rc=r || c
b=box.rc /*what box is this R,C in ?*/
rowlb.r=min(rowlb.r,b) /*find min box # for row R.*/
collb.c=min(collb.c,b) /*find min box # for col C.*/
boxlr.b=min(boxlr.b,r) /*find min row # for box B.*/
boxlc.b=min(boxlc.b,c) /*find min col # for box B.*/
end /*c*/
end /*r*/
 
do j=1 to 9 /*for each box, row, col...*/
rowhb.j=rowlb.j+2 /*compute row's high box #.*/
colhb.j=collb.j+6 /*compute col's high box #.*/
boxhr.j=boxlr.j+2 /*compute box's high row #.*/
boxhc.j=boxlc.j+6 /*compute box's high col #.*/
end /*j*/
 
if showgrid then call showgrid 'the puzzle' /*show the grid to screen ?*/
if \validall() then exit /*validate specified digits*/
tellinvalid=0 /*don't tell err messages. */
!.= /*nullify valid empty# list*/
call buildposs /*build possible values. */
if showposs then call showgrid 'puzzle possibles' /*show 1st possibles?*/
if \validate(1) then exit /*validate the puzzle. */
 
if showoneline then do /*show grid as line line ? */
_= /*start with a clean slate.*/
do r=1 for 9
do c=1 for 9
_=_ || @.r.c /*build the string ... */
end /*c*/
end /*r*/
 
_=translate(strip(_,'T'),".",' ')
if showinfo then call $T 'one-line grid:'
call $T _
end
 
if aprune |,
showposs then do
call pruneposs /*go build poss, then prune*/
if showposs then call showgrid 'possibles' /*show grid.*/
if \validate(1) then exit /*validate the puzzle. */
end
 
if combos==1 then call $t sod 'puzzle solved.'
else if showcomb then call $t 'combinations='comma(combos)
exit /*stick a fork in it, we're done.*/
 
/*─────────────────────────────vern subroutine──────────────────────────*/
vern: parse arg v,w /*verify a digit for an opt*/
if v=='' then call er 35,v w
if \isInt(v) then call er 92,v w
if v<1 | v>9 then call er 81,1 9 v w
return
 
/*─────────────────────────────buildposs subroutine─────────────────────*/
buildposs: !.= /*nullify possibilities. */
combos=1
 
do rp=1 for 9 /*build table of valid #s. */
do cp=1 for 9 /*step through each column.*/
if @.rp.cp\==' ' then iterate /*not blank? Keep looking.*/
 
do jd=1 for 9 /*try each digit. */
@.rp.cp=jd
if validx(rp,cp) then !.rp.cp=!.rp.cp || jd
end /*jd*/
 
combos=combos*length(!.rp.cp) /*calculate # combinations.*/
@.rp.cp=' ' /*restore the point (blank)*/
end /*cp*/
end /*rp*/
 
return
 
/*─────────────────────────────showgrid subroutine──────────────────────*/
showgrid: parse arg title
if clear then !cls /*clear the screen ? */
if title\=='' & showinfo then call $t !fn 'is showing' title
gtail=copies3(gridlb || gridlin || copies2(griduj || gridlin) || gridrb)
ghead=copies3(gridlt || gridlin || copies2(griddj || gridlin) || gridrt)
call tg ghead
gemp=copies3(copies3(gridbar || gridemp)gridbar)
grid=copies3(gridlj || gridlin || copies2(gridcross || gridlin)gridrj)
anyshow= \ ((showcell || showcol || showrow || showbox)\=='')
 
do jr=1 for 9
if \short then call tg gemp
gnum=
 
do jc=1 for 9
[email protected].jr.jc
if _\==' ' & highLight then _=hLl || _ || hLr
 
if _==' ' & ,
showposs then do
jrjc=jr || jc
showit=anyshow
if showcell\=='' then if wordpos(jrjc,showcell)\==0 then showit=1
if showcol\=='' then if pos(jc,showcol)\==0 then showit=1
if showrow\=='' then if pos(jr,showrow)\==0 then showit=1
 
do jb=1 while showbox\==''
b=substr(showbox,jb,1)
if b==' ' then leave
if wordpos(jrjc,box.b)\==0 then showit=1
end /*jb*/
 
if showit then _=strip(left(!.jr.jc,gridwidth),'T')
end
 
gnum=gnum || gridbar || centre(_,gridwidth)
if jc//3==0 then gnum=gnum || gridbar
end /*jc*/
 
call tg gnum
if \short then call tg gemp
 
if jr//3==0 then do
call tg gtail
if jr\==9 then call tg ghead
end
else call tg grid
end /*jr*/
 
call $t
return
 
/*─────────────────────────────validate subroutine──────────────────────*/
validate: /*are all empties possible?*/
 
do r=1 for 9 /*step through each row. */
do c=1 for 9 /*step through each column.*/
 
if @.r.c==' ' & ,
 !.r.c=='' then do /*no legal digit here. */
if arg(1)==1 then call $t sod "puzzle isn't valid !"
return 0
end
end /*c*/
end /*r*/ /*sub requires possibles. */
 
return 1 /*indicate puzzle is valid.*/
 
/*─────────────────────────────validall subroutine──────────────────────*/
validall: /*validate all Q specified.*/
 
do r=1 for 9 /*step through each row. */
do c=1 for 9 /*step through each column.*/
if @.r.c==' ' then iterate /*if blank, then it's ok. */
y= /*the rest of the row. */
rc=r||c
do kc=1 for 9 /*compare to #s in column. */
if kc\==c then y=y|| @.r.kc /*build the rest of the row*/
end /*kc*/
[email protected].r.c
if pos(q,y)\==0 then return tem(r,c,'row') /*same # in same row?*/
y= /*the rest of the column. */
do kr=1 for 9 /*compare to #s in column. */
if kr\==r then y=y || @.kr.c /*build the rest of the col*/
end /*kr*/
 
if pos(q,y)\==0 then return tem(r,c,'col') /*same # in same col?*/
y= /*the rest of the box. */
b=box.rc
 
do br=boxr.b to boxr.b+2 /*compare to #s of the box.*/
do bc=boxc.b to boxc.b+2 /*build the rest of the box*/
if br\==r & bc\==c then y=y || @.br.bc
end /*bc*/
end /*br*/
 
if pos(q,y)\==0 then return tem(r,c,'box') /*same # in same box?*/
end /*c*/
end /*r*/
 
return 1 /*indicate all are valid.*/
 
/*─────────────────────────────validx subroutine────────────────────────*/
validx: arg r,c
rc=r || c
y= /*the rest of the row. */
do kc=1 for 9 /*compare to #s in column. */
if kc\==c then y=y || @.r.kc /*build the rest of the row*/
end /*kc*/
 
[email protected].r.c /*get the digit at r,c */
if pos(q,y)\==0 then return tem(r,c,'row') /*same number in same row ?*/
y= /*the rest of the column. */
do kr=1 for 9 /*compare to #s in column. */
if kr\==r then y=y || @.kr.c /*build the rest of the col*/
end /*kr*/
 
if pos(q,y)\==0 then return tem(r,c,'col') /*same # in same column ?*/
y= /*the rest of the box. */
b=box.rc
 
do br=boxr.b to boxr.b+2 /*compare to #s of the box.*/
do bc=boxc.b to boxc.b+2 /*build the rest of the box*/
if br==r & bc==c then iterate
y=y || @.br.bc
end /*br*/
end /*bc*/
 
if pos(q,y)\==0 then return tem(r,c,'box') /*same # in same box ? */
return 1 /*indicate X (r,c) is valid*/
 
/*─────────────────────────────pruneposs subroutine─────────────────────*/
pruneposs: if \(prunesing | pruneexcl | prunemats | pruneline) then return
call buildposs
 
do prunes=1
call $t !fn 'is starting prune pass #' prunes
found=0 /*indicate no prunes so far*/
 
if prunesing then do /*prune puzzle for singles.*/
_=prunesing() /*find any singles ? */
found=found | _ /*track if anything found. */
if _ then if showgrid then call showgrid /*show grid*/
end
 
if pruneexcl then do /*prune puzzle for singles.*/
_=pruneexcl() /*find any excluives ? */
found=found | _ /*track if anything found. */
if _ then if showgrid then call showgrid /*show grid*/
end
 
if pruneonly then do /*prune puzzle for onlys. */
_=pruneonly() /*find any onlys ? */
found=found | _ /*track if anything found. */
if _ then if showgrid then call showgrid /*show grid*/
end
 
if prunemats then do jpm=2 to 8 /*prune puzzle for matches.*/
_=prunemats(jpm) /*find any matches (len=j)?*/
found=found | _ /*track if anything found. */
if _ then if showgrid then call showgrid /*show grid*/
end
 
if pruneline then do /*prune puzzle for lines. */
_=pruneline() /*find 2 or more on a line?*/
found=found | _ /*track if anything found. */
if _ then if showgrid then call showgrid /*show grid*/
end
 
if \found then leave /*nothing found this time ?*/
end /*prunes*/
 
return
 
/*─────────────────────────────prunesing subroutine─────────────────────*/
prunesing: foundsing=0
 
do r=1 for 9
do c=1 for 9
_=length(!.r.c) /*get length of possible. */
if _==0 then iterate /*if null, then ignore it. */
if _\==1 then iterate /*if not one digit, ignore.*/
@.r.c=!.r.c /*it's 1 digit, a solution.*/
 !.r.c= /*erase the old possible. */
foundsing=1
call $t !fn 'found a single digit at cell' drc(r,c,@.r.c)
end /*c*/
end /*r*/
 
if foundsing then call buildposs /*re-build the possibles. */
return foundsing
 
/*─────────────────────────────pruneexcl subroutine─────────────────────*/
pruneexcl: foundexcl=0
 
do exclusives=1 /*keep building possibles. */
do r=1 for 9
do c=1 for 9
z=!.r.c
lz=length(z) /*get length of possible. */
if lz==0 then iterate /*if null, then ignore it. */
y=
rc=r || c
b=box.rc
 
do br=boxr.b to boxr.b+2 /*compare to #s of the box.*/
do bc=boxc.b to boxc.b+2 /*build the rest of the box*/
if br==r & bc==c then iterate
y=y || @.br.bc || !.br.bc
end /*bc*/
end /*br*/
 
/*test for reduction. */
do t=1 for lz
q=substr(z,t,1)
 
if pos(q,y)==0 then do
foundexcl=1
@.r.c=q /*it's a singularity, a sol*/
 !.r.c= /*erase old possibleity. */
call $t !fn 'found the digit' q,
"by exclusiveness at cell" drc(r,c,z)
call buildposs /*re-build the possibles. */
iterate exclusives
end
end /*t*/
end /*c*/
end /*r*/
 
leave
end /*exclusives*/
 
return foundexcl
 
/*─────────────────────────────prunemats subroutine─────────────────────*/
prunemats: foundmatch=0 /*no matches found so far. */
parse arg L /*length of match, L=2,pair*/
 
do matches=1
do r=1 for 9
do c=1 for 9
_=length(!.r.c) /*get length of possible. */
if _==0 then iterate /*if null, then ignore it. */
if _\==L then iterate /*not right length, ignore.*/
qq=!.r.c
m=0 /*count of matches so far. */
do _c=1 for 9 /*nother match in same row?*/
if qq==!.r._c then m=m+1 /*up count if it's a match.*/
end /*_c*/
 
if m>=L then do pc=1 for 9 /*squish other possibles. */
old=!.r.pc /*save the "old" value. */
if old==qq then iterate /*if match, then ignore it.*/
if old=='' then iterate /*if null poss, then ignore*/
new=squish(old,qq) /*remove mat's digs from X.*/
if new==old then iterate /*if no change,keep looking*/
 !.r.pc=new /*store new value into old.*/
foundmatch=1 /*indicate match was found.*/
call $t !fn 'is removing a' old "from" drc(r,pc,old),
'because of a match at' drc(r,c,qq)
if length(new)==1 then do /*reduce if L=1*/
@.r.pc=new /*store single.*/
 !.r.pc= /*delete poss. */
call buildposs /*re-build poss*/
iterate matches /*start over.*/
end
end /*pc*/
m=0 /*count of matches so far. */
 
do _r=1 for 9 /*nother match in same col?*/
if qq==!._r.c then m=m+1 /*up count if it's a match.*/
end /*_r*/
 
if m>=L then do pr=1 for 9 /*squish other possibles. */
old=!.pr.c /*save the "old" value. */
if old==qq then iterate /*if match, then ignore it.*/
if old=='' then iterate /*if null poss, then ignore*/
new=squish(old,qq) /*remove mat's digs from X.*/
if new==old then iterate /*if no change,keep looking*/
 !.pr.c=new /*store new value into old.*/
foundmatch=1 /*indicate match was found.*/
call $t !fn 'is removing a' old "from" drc(pr,c,old),
'because of a match at' drc(r,c,qq)
if length(new)==1 then do /*reduce if L=1*/
@.pr.c=new /*store single.*/
 !.pr.c= /*delete poss. */
call buildposs /*re-build poss*/
iterate matches /*start over.*/
end
end /*pr*/
end /*c*/
end /*r*/
 
leave
end /*matches*/
 
return foundmatch
 
/*─────────────────────────────pruneonly subroutine─────────────────────*/
pruneonly: foundmatch=0 /*no matches found so far. */
 
do findonlys=1 /*keep searching ... */
_row.= /*build str for each row . */
 
do r=1 for 9
do c=1 for 9
if !.r.c\=='' then _row.r=_row.r !.r.c
end /*c*/
end /*r*/
 
_col.= /*build str for each boxcol*/
 
do c=1 for 9
do r=1 for 9
if !.r.c\=='' then _col.c=_col.c !.r.c
end /*r*/
end /*c*/
 
do r=1 for 9
do c=1 for 9
q=!.r.c
if q=='' then iterate /*if empty, then ignore it.*/
 
do j=1 to length(q) /*step through each digit. */
k=substr(q,j,1)
 
if kount1(k,_row.r) |, /*is this the ONLY digit K?*/
kount1(k,_col.c) then do i=1 to length(q) /*prune others.*/
foundmatch=1
_=substr(q,i,1)
if _==k then iterate /*if=K, ignore.*/
o=squish(q,_) /*remove others*/
 !.r.c=o
call $t !fn 'removed part of an only',
_ "from cell" drc(r,c,q)
if length(o)==1 then /*reduce if L=1*/
do
@.r.c=o /*store single.*/
 !.r.c= /*delete poss. */
call buildposs /*re-build poss*/
iterate findonlys /*start over. */
end
end /*i*/
end /*j*/
end /*c*/
end /*r*/
 
leave
end /*findonlys*/
 
return foundmatch
 
/*─────────────────────────────pruneline subroutine─────────────────────*/
pruneline: foundmatch=0 /*no matches found so far. */
 
do findlines=1 /*keep searching ... */
_boxr.= /*build str for each boxrow*/
 
do r=1 for 9
do c=1 for 9
rc=r || c
b=box.rc
if !.r.c\=='' then _boxr.r.b=strip(_boxr.r.b !.r.c)
end /*c*/
end /*r*/
 
_boxc.= /*build str for each boxcol*/
 
do c=1 for 9
do r=1 for 9
rc=r || c
b=box.rc
if !.r.c\=='' then _boxc.c.b=strip(_boxc.c.b !.r.c)
end /*r*/
end /*c*/
 
do r=1 for 9 /*search all rows for twins*/
 
do b=rowlb.r to rowhb.r /*for each row, search box.*/
aline=_boxr.r.b /*get a row in the box. */
if aline=='' then iterate /*if empty, ignore the line*/
w=words(aline) /*W is # of words in aline*/
if w<2 then iterate /*if < 2 words, ignore line*/
 
do k=1 for 9 /*search for each digit. */
f=pos(k,aline) /*pos of the 1st digit: k */
if f==0 then iterate /*no dig k, so keep looking*/
s=pos(k,aline,f+1) /*pos of the 2nd digit: k */
if s==0 then iterate /*no 2nd k, so keep looking*/
 
do jr=rowlb.r to rowhb.r /*look at the other 2 rows.*/
if jr==r then iterate /*if the same row, ignore. */
if pos(k,_boxr.jr.b)\==0 then iterate k /*if no digit K, ignore*/
end /*jr*/
/*found 2 Ks in row R box B*/
do jb=rowlb.r to rowhb.r /*search boxes row R for K.*/
if jb==b then iterate /*ignore if in the same box*/
if pos(k,_boxr.r.jb)==0 then iterate
foundmatch=1 /*found a K in col C box JB*/
 
do kc=1 for 9 /*find which cell K is in.*/
rc=r || kc
if box.rc==b then iterate /*ignore if in the same box*/
_=!.r.kc
if _=='' then iterate /*ignore if no possible. */
if pos(k,_)==0 then iterate /*if no digit K, ignore. */
call $t  !fn 'is row-line pruning digit' k,
'from cell' drc(r,kc,!.r.kc)
 !.r.kc=squish(_,k) /*remove mat's digs from X.*/
if length(!.r.kc)==1 then do /*pruned down to one digit?*/
@.r.kc=!.r.kc /*make a true digit*/
 !.r.kc= /*erase possibility*/
call buildposs /*rebuild possibles*/.
iterate findlines
end
end /*kc*/
end /*jb*/
end /*k*/
end /*b*/
end /*r*/
 
do c=1 for 9 /*search all cols for twins*/
 
do b=collb.c to colhb.c by 3 /*for each col, search box.*/
aline=_boxc.c.b /*get a column in the box.*/
if aline=='' then iterate /*if empty, ignore line*/
w=words(aline)
if w<2 then iterate /*if < 2 words, ignore line*/
 
do k=1 for 9 /*search for each digit. */
f=pos(k,aline) /*pos of the 1st digit: k */
if f==0 then iterate /*no dig k, so keep looking*/
s=pos(k,aline,f+1) /*pos of the 2nd digit: k */
if s==0 then iterate /*no 2nd k, so keep looking*/
 
do jc=boxlc.b to boxhc.b /*look at the other 2 cols.*/
if jc==c then iterate /*if the same col, ignore. */
if pos(k,_boxc.jc.b)\==0 then iterate k /*if no digit K, ignore*/
end /*jc*/
/*found 2 Ks in col C box B*/
do jb=collb.c to colhb.c by 3 /*search boxes col C for K.*/
if jb==b then iterate /*ignore if in the same box*/
if pos(k,_boxc.c.jb)==0 then iterate
foundmatch=1 /*found a K in col C box JB*/
 
do kr=1 for 9 /*find which cell K is in.*/
rc=kr || c
if box.rc==b then iterate /*ignore if in the same box*/
_=!.kr.c
if _=='' then iterate /*ignore if no possible. */
if pos(k,_)==0 then iterate /*if no digit K, ignore. */
call $t !fn 'is col-line pruning digit' k,
'from cell' drc(kr,c,!.kr.c)
 !.kr.c=squish(_,k) /*remove mat's digs from X.*/
if length(!.kr.c)==1 then do /*pruned down to one digit?*/
@.kr.c=!.kr.c /*make a true digit*/
 !.kr.c= /*erase possibility*/
call buildposs /*rebuild possibles*/.
iterate findlines
end
end /*kr*/
end /*jb*/
end /*k*/
end /*b*/
end /*c*/
 
leave
end /*findlines*/
 
return foundmatch
 
/*────────────────────────────────────────────────────────────────────────────*/
commas: procedure; parse arg _; n=_'.9'; #=123456789; b=verify(n,#,"M")
e=verify(n,#'0',,verify(n,#"0.",'M'))-4
do j=e to b by -3; _=insert(',',_,j); end /*j*/; return _
/*═════════════════════════════general 1-line subs══════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════*/
!all:  !!=!;!=space(!);upper !;call !fid;!nt=right(!var('OS'),2)=='NT';!cls=word('CLS VMFCLEAR CLRSCREEN',1+!cms+!tso*2);if arg(1)\==1 then return 0;if wordpos(!,'? ?SAMPLES ?AUTHOR ?FLOW')==0 then return 0;!call=']$H';call '$H' !fn !;!call=;return 1
!cal: if symbol('!CALL')\=="VAR" then !call=; return !call
!env:  !env='ENVIRONMENT'; if !sys=='MSDOS' | !brexx | !r4 | !roo then !env='SYSTEM'; if !os2 then !env='OS2'!env; !ebcdic=1=='f0'x; if !crx then !env='DOS'; return
!fid: parse upper source !sys !fun !fid . 1 . . !fn !ft !fm .; call !sys; if !dos then do; _=lastpos('\',!fn); !fm=left(!fn,_); !fn=substr(!fn,_+1); parse var !fn !fn '.' !ft; end; return word(0 !fn !ft !fm,1+('0'arg(1)))
!rex: parse upper version !ver !vernum !verdate .; !brexx='BY'==!vernum; !kexx='KEXX'==!ver; !pcrexx='REXX/PERSONAL'==!ver | 'REXX/PC'==!ver; !r4='REXX-R4'==!ver; !regina='REXX-REGINA'==left(!ver,11); !roo='REXX-ROO'==!ver; call !env; return
!sys:  !cms=!sys=='CMS'; !os2=!sys=='OS2'; !tso=!sys=='TSO' | !sys=='MVS'; !vse=!sys=='VSE'; !dos=pos('DOS',!sys)\==0 | pos('WIN',!sys)\==0 | !sys=='CMD'; !crx=left(!sys,6)=='DOSCRX'; call !rex; return
!var: call !fid; if !kexx then return space(dosenv(arg(1))); return space(value(arg(1),,!env))
$fact!: procedure; parse arg x _ .; l=length(x); n=l-length(strip(x,'T',"!")); if n<=-n | _\=='' | arg()\==1 then return x; z=left(x,l-n); if z<0 | \isInt(z) then return x; return $fact(z,n)
$fact: procedure; parse arg x _ .; arg ,n ! .; n=p(n 1); if \isInt(n) then n=0; if x<-n | \isInt(x) | n<1 | _ || !\=='' | arg()>2 then return x || copies("!",max(1,n)); !=1; s=x//n; if s==0 then s=n; do j=s to x by n; !=!*j; end; return !
$sfxa: parse arg ,s,m; arg u,c; if pos(left(s,2),u)\==0 then do j=length(s) to compare(s,c)-1 by -1; if right(u,j)\==left(c,j) then iterate; _=left(u,length(u)-j); if isNum(_) then return m*_; leave; end; return arg(1)
$sfxf: parse arg y; if right(y,1)=='!' then y=$fact!(y); if \isNum(y) then y=$sfxz(); if isNum(y) then return y; return $sfxm(y)
$sfxm: parse arg z; arg w; b=1000; if right(w,1)=='I' then do; z=shorten(z); w=z; upper w; b=1024; end; p=pos(right(w,1),'KMGTPEZYXWVU'); if p==0 then return arg(1); n=shorten(z); r=num(n,f,1); if isNum(r) then return r*b**p; return arg(1)
$sfxz: return $sfxa($sfxa($sfxa($sfxa($sfxa($sfxa(y,'PAIRs',2),'DOZens',12),'SCore',20),'GREATGRoss',1728),'GRoss',144),'GOOGOLs',1e100)
$t: if tops=='' then say arg(1); else do; !call=']$T'; call "$T" tops arg(1); !call=; end; return
ab: arg ab,abl; return abbrev(ab,_,abl)
abb: arg abbu; parse arg abb; return abbrev(abbu,_,abbl(abb))
abbl: return verify(arg(1)'a',@abc,'M')-1
abbn: parse arg abbn; return abb(abbn) | abb('NO'abbn)
abn: arg ab,abl; return abbrev(ab,_,abl) | abbrev('NO'ab,_,abl+2)
copies2: return copies(arg(1),2)
copies3: return copies(arg(1),3)
drc: procedure; parse arg r,c,p; _=r","c; if p\=='' then _=_ "("p')'; return _
er: parse arg _1,_2; call '$ERR' "14"p(_1) p(word(_1,2) !fid(1)) _2; if _1<0 then return _1; exit result
err: call er '-'arg(1),arg(2); return ''
erx: call er '-'arg(1),arg(2); exit ''
halt: call er .1
int: int=num(arg(1),arg(2)); if \isInt(int) then call er 92,arg(1) arg(2); return int/1
isInt: return datatype(arg(1),'W')
isNum: return datatype(arg(1),'N')
kount1: parse arg qd,string; k1=pos(qd,string); if k1==0 then return 0; return pos(qd,string,k1+1)==0
lower: return translate(arg(1),@abc,translate(@abc))
na: if arg(1)\=='' then call er 01,arg(2); parse var ops na ops; if na=='' then call er 35,_o; return na
nai: return int(na(),_o)
nail: return squish(int(translate(na(),0,','),_o))
no: if arg(1)\=='' then call er 01,arg(2); return left(_,2)\=='NO'
noValue:!sigl=sigl; call er 17,!fid(2) !fid(3) !sigl condition('D') sourceline(!sigl)
num: procedure; parse arg x .,f,q; if x=='' then return x; if isNum(x) then return x/1; x=space(translate(x,,','),0); if \isNum(x) then x=$sfxf(x); if isNum(x) then return x/1; if q==1 then return x; if q=='' then call er 53,x f; call erx 53,x f
p: return word(arg(1),1)
shorten:procedure; parse arg a,n; return left(a,max(0,length(a)-p(n 1)))
simple: return translate(arg(1),'.||--%<>AV'copies('+',25),"·│║─═☼◄►↑↓┤┐└┴┬├┼┘┌╔╗╚╝╟╢╞╡╫╪╤╧╥╨╠╣")
squish: return space(translate(arg(1),,word(arg(2) ',',1)),0)
syntax: !sigl=sigl; call er 13,!fid(2) !fid(3) !sigl !cal() condition('D') sourceline(!sigl)
tem: parse arg r,c,w; if tellInvalid then say '***error!*** row' r", col" c '('@.r.c") is a duplicate of another in the same" w'.'; return 0
tg: arg tg; if simple then tg=simple(tg); call $t gridindent || tg; return


This REXX program makes use of   $ERR.REX   REXX program which is used to write (display) error messages to the terminal screen, with supplemental text that identifies what program issued the error, and in some cases, also identifies the failing REXX statement and some particulars about the failure.

The   $ERR.T.REX   REXX program can be found here   ───►   $ERR.REX.

changestr [email protected]@@@@@@@@@@@@@@@@@@@@@@@##############%%%%%%%%%%%%%%%%%%%

output:
$SUDOKU is showing the puzzle
   ┌───────┬───────┬───────┐┌───────┬───────┬───────┐┌───────┬───────┬───────┐
   │       │       │       ││       │       │       ││       │       │       │
   │       │   5   │       ││       │   7   │       ││   8   │   9   │       │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   9   │       │       ││       │   3   │       ││       │       │       │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   1   │       │       ││       │   8   │   9   ││       │   4   │       │
   │       │       │       ││       │       │       ││       │       │       │
   └───────┴───────┴───────┘└───────┴───────┴───────┘└───────┴───────┴───────┘
   ┌───────┬───────┬───────┐┌───────┬───────┬───────┐┌───────┬───────┬───────┐
   │       │       │       ││       │       │       ││       │       │       │
   │       │       │   9   ││       │       │       ││       │       │   1   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │       │       │   1   ││   3   │       │   5   ││   2   │       │       │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   6   │       │       ││       │       │       ││   5   │       │       │
   │       │       │       ││       │       │       ││       │       │       │
   └───────┴───────┴───────┘└───────┴───────┴───────┘└───────┴───────┴───────┘
   ┌───────┬───────┬───────┐┌───────┬───────┬───────┐┌───────┬───────┬───────┐
   │       │       │       ││       │       │       ││       │       │       │
   │       │   6   │       ││   8   │   9   │       ││       │       │   3   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │       │       │       ││       │   5   │       ││       │       │   7   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │       │   9   │   8   ││       │   2   │       ││       │   5   │       │
   │       │       │       ││       │       │       ││       │       │       │
   └───────┴───────┴───────┘└───────┴───────┴───────┘└───────┴───────┴───────┘

$SUDOKU is starting prune pass # 1
$SUDOKU found the digit 8 by exclusiveness at cell 2,2 (2478)
$SUDOKU found the digit 3 by exclusiveness at cell 3,7 (367)
$SUDOKU found the digit 5 by exclusiveness at cell 4,1 (234578)
$SUDOKU found the digit 8 by exclusiveness at cell 5,1 (478)
$SUDOKU found the digit 9 by exclusiveness at cell 6,4 (12479)
$SUDOKU found the digit 9 by exclusiveness at cell 5,9 (469)
$SUDOKU found the digit 5 by exclusiveness at cell 7,3 (2457)
$SUDOKU found the digit 1 by exclusiveness at cell 8,2 (1234)
$SUDOKU found the digit 9 by exclusiveness at cell 8,7 (469)
$SUDOKU found the digit 8 by exclusiveness at cell 8,8 (268)
$SUDOKU found the digit 8 by exclusiveness at cell 6,9 (48)
$SUDOKU found the digit 8 by exclusiveness at cell 4,6 (24678)
$SUDOKU found the digit 4 by exclusiveness at cell 4,7 (467)
$SUDOKU found the digit 2 by exclusiveness at cell 7,8 (12)
$SUDOKU found the digit 4 by exclusiveness at cell 9,9 (46)
$SUDOKU found the digit 6 by exclusiveness at cell 9,7 (16)
$SUDOKU found the digit 1 by exclusiveness at cell 7,7 (1)
$SUDOKU found the digit 1 by exclusiveness at cell 2,8 (167)
$SUDOKU found the digit 7 by exclusiveness at cell 2,7 (7)
 ∙
 ∙
 ∙
   some output elided ∙∙∙
 ∙
 ∙
 ∙ 
   ┌───────┬───────┬───────┐┌───────┬───────┬───────┐┌───────┬───────┬───────┐
   │       │       │       ││       │       │       ││       │       │       │
   │   4   │   5   │   3   ││   1   │   7   │   6   ││   8   │   9   │   2   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   9   │   8   │   6   ││   4   │   3   │   2   ││   7   │   1   │   5   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   1   │   2   │   7   ││   5   │   8   │   9   ││   3   │   4   │   6   │
   │       │       │       ││       │       │       ││       │       │       │
   └───────┴───────┴───────┘└───────┴───────┴───────┘└───────┴───────┴───────┘
   ┌───────┬───────┬───────┐┌───────┬───────┬───────┐┌───────┬───────┬───────┐
   │       │       │       ││       │       │       ││       │       │       │
   │   5   │   3   │   9   ││   2   │   6   │   8   ││   4   │   7   │   1   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   8   │   7   │   1   ││   3   │   4   │   5   ││   2   │   6   │   9   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   6   │   4   │   2   ││   9   │   1   │   7   ││   5   │   3   │   8   │
   │       │       │       ││       │       │       ││       │       │       │
   └───────┴───────┴───────┘└───────┴───────┴───────┘└───────┴───────┴───────┘
   ┌───────┬───────┬───────┐┌───────┬───────┬───────┐┌───────┬───────┬───────┐
   │       │       │       ││       │       │       ││       │       │       │
   │   7   │   6   │   5   ││   8   │   9   │   4   ││   1   │   2   │   3   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   2   │   1   │   4   ││   6   │   5   │   3   ││   9   │   8   │   7   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   3   │   9   │   8   ││   7   │   2   │   1   ││   6   │   5   │   4   │
   │       │       │       ││       │       │       ││       │       │       │
   └───────┴───────┴───────┘└───────┴───────┴───────┘└───────┴───────┴───────┘

$SUDOKU is starting prune pass # 4
 sudoku puzzle solved.

REXX version 2[edit]

{{trans|PL/I]]

  Parse Arg g.0fid
Select
When g.0fid='?' Then Do
Say 'This program solves any (valid) SUDOKU puzzle'
Say 'Specify the name of the file containing the puzzle as argument'
Exit
End
When g.0fid='' Then
Call exit 'no input specified'
When lines(g.0fid)=0 Then
Call exit 'specified input does not exist'
Otherwise
Nop
End
instr=''
Do While lines(g.0fid)>0
instr=instr||linein(g.0fid)
End
Call lineout g.0fid
digits='123456789'
buffer=translate(instr,digits'000',digits'0.x'||xrange('00'x,'ff'x))
buffer=space(buffer,0)
If length(buffer)<>81 Then
Call exit 'invalid input from file' g.0fid
Call set_geometry
 
posbit.=copies('0',9)
z=posbit.0
d.z=0
 
Do i=1 To 9
posbit.i=overlay('1',posbit.i,i,1)
z=posbit.i
d.z=i
End
 
Do r=1 To 9
Do c=1 To 9
Parse Var buffer d +1 buffer
matrix.r.c=posbit.d
End
End
 
nn=0
Call show_matrix 'input from' g.0fid
res=solve()
If res Then Do
Call dbg 'nn='format(nn,5) 'res='res
Call show_matrix 'solution'
End
Else
Say 'impossible'
Exit
 
solve: Procedure Expose g. matrix. posbit. nn box. boxlr. boxlc.
nn=nn+1
Call dbg 'solve nn='format(nn,5)
do i = 1 to 9
do j = 1 to 9
if matrix.i.j=posbit.0 Then
Leave i
End
End
If i>9 Then Do
do i = 1 to 9
do j = 1 to 9
k = pos('1',matrix.i.j)
Call dbg 'sudoku',
Format(nn,9) Format(i,9) Format(j,9) Format(k,9)
matrix.i.j=posbit.0
result_=neg(or(any_col(i),any_row(j),any_box(i,j)))
If substr(result_,k,1)=0 Then
Return 0
matrix.i.j=posbit.k
End
End
Return 1
End
Else Do
result_=neg(or(any_col(i),any_row(j),any_box(i,j)))
Call dbg 'resulta='result_
k=0;
do Until k=0
Call dbg 'resultb='result_
k=pos('1',result_,k+1)
Call dbg 'k='Format(k,2)Format(i,2)Format(j,2)
if k>0 then Do;
matrix.i.j=posbit.k
Call dbg 'setting matrix('i','j')->'k
res=solve()
Call dbg 'A nn='format(nn,5) 'res='res
if res then
return 1
else Do;
matrix.i.j=posbit.0
Call dbg 'setting matrix('i','j')->'0
End;
end;
end;
return 0
end;
 
set_geometry:
box.=''
Do j=1 To 9 /* build the box bounds. */
rr=(((j*3)%10)+1)*3-2 /* compute row lower bound. */
cc=(((j-1)//3)+1)*3-2 /* compute col lower bound. */
boxr.j=rr
boxc.j=cc
Do r=rr To rr+2 /* build boxes with cell #s. */
Do c=cc To cc+2
box.r.c=j
End
End
End /* j */
rowlb.=10 /* row R, low box number=b. */
collb.=10 /* col R, low box number=b. */
boxlr.=10 /* box B, low row number=r. */
boxlc.=10 /* box B, low col number=c. */
 
Do r=1 To 9
Do c=1 To 9
b=box.r.c /* what box is this R,C in ? */
rowlb.r=min(rowlb.r,b) /* find min box # for row R. */
collb.c=min(collb.c,b) /* find min box # for col C. */
boxlr.b=min(boxlr.b,r) /* find min row # for box B. */
boxlc.b=min(boxlc.b,c) /* find min col # for box B. */
End
End
Return
 
any_col: Procedure Expose matrix.
Parse Arg r
res='000000000'
Do c=1 To 9
p=pos('1',matrix.r.c)
If p>0 Then
res=overlay('1',res,p,1)
End
Return res
 
any_row: Procedure Expose matrix.
Parse Arg c
res='000000000'
Do r=1 To 9
p=pos('1',matrix.r.c)
If p>0 Then
res=overlay('1',res,p,1)
End
Return res
 
any_box: Procedure Expose matrix. box. boxlr. boxlc.
Parse Arg r,c
b=box.r.c
res='000000000'
Do r=boxlr.b For 3
Do c=boxlc.b For 3
p=pos('1',matrix.r.c)
If p>0 Then
res=overlay('1',res,p,1)
End
End
Return res
 
or: Procedure
res='000000000'
Do ia=1 To 3
a=arg(ia)
Do p=1 To 9
If substr(a,p,1)=1 Then
res=overlay('1',res,p,1)
End
End
Return res
 
neg: Procedure
Parse Arg s
res=''
Do p=1 To 9
If substr(s,p,1)=1 Then
res=res'0'
Else
res=res'1'
End
Return res
 
o: Say arg(1)
Return
 
show_matrix:
Call o arg(1)
Do r=1 To 9
ol=''
Do c=1 To 9
m=matrix.r.c
ol=ol||d.m' '
If c//3=0 Then
ol=ol' '
End
Call o ol
If r//3=0 Then
Call o ' '
End
Return
 
dbg:
If debug=1 Then
Say arg(1)
Return
 
exit: Say '*ERROR*' arg(1)
Output:
input from d:\_sudoku\in\sdk001.in
4 6 0  0 0 1  0 0 0
0 0 2  0 9 6  0 0 0
0 3 0  0 0 0  0 6 8

0 0 0  0 0 0  0 3 7
0 0 0  6 0 7  0 0 0
5 1 0  0 0 0  0 0 0

8 4 0  0 0 0  0 5 0
0 0 0  7 1 0  9 0 0
0 0 0  3 0 0  0 2 4

solution
4 6 5  8 3 1  2 7 9
7 8 2  4 9 6  3 1 5
1 3 9  5 7 2  4 6 8

6 9 4  1 2 5  8 3 7
3 2 8  6 4 7  5 9 1
5 1 7  9 8 3  6 4 2

8 4 1  2 6 9  7 5 3
2 5 3  7 1 4  9 8 6
9 7 6  3 5 8  1 2 4

REXX version 3[edit]

This is version 1 (thanks) cut to the essentials, restructured, and modified

/* REXX ---------------------------------------------------------------
* program to solve nearly every SUDOKU puzzle
* using a number of strategies learned from REXX version 1
* and one rather efficient algorithm created by me: prunewalt
* see solve: for details
* Tested with Regina and ooRexx
* See version 2 for a program that solves every valid SUDOKU
*--------------------------------------------------------------------*/

Signal on Halt
Signal on Novalue
Signal on Syntax
Parse Arg fid debug
Select
When fid='?' Then Do
Say 'This program solves many (nearly every?) SUDOKU puzzle'
Say 'rexx sudoku file [DEBUG]'
Say 'Input: file.in'
Say 'Debug: file.dbg'
Say 'Known: file.sol'
Say 'Incomplete solution (if applicable): fileF.in'
Say 'Output: on screen'
Say 'Adapt subroutine get_input if necessary!'
Say 'See version 2 for a brute force program',
'solving EVERY valid SUDOKU'
Exit
End
When fid='' Then Do
Say 'Input file not specified'
Say 'Enter "rexx sudoku ?" for help'
Exit
End
Otherwise
Nop
End
 
g.=0
g.0debug=(translate(debug)='DEBUG')
 
Call get_input fid /* get input and set up file names */
/* Please adapt to your environment */
Numeric Digits 50 /* because of huge # of combinations */
 
Call set_geometry
 
Call show_aa 'the puzzle' /* show the grid to screen */
Call build_poss /* build possible values */
g.0todo_init=g.0todo
Call show_poss 'puzzle possibles' /* show 1st possibles */
 
Call solve /* now try to solve it */
 
If g.0todo=0 Then Do /* no cell left empty */
Call o g.0fid 'puzzle solved.' /* tell it */
Call o left(g.0fid,12) 'puzzle solved.'
Call show_aa 'solved' /* show the solution */
End
Else Do /* some cells couldn't be filled */
Call show_poss 'failed' /* show the possibilities left */
Call o left(g.0fid,12) 'puzzle failed g.0todo='g.0todo
Call show_aa 'failed','.' /* show the partly solved puzzle */
End
 
Call write_summary
 
Exit
 
build_poss: Procedure Expose g. s. aa. poss.,
box. boxr. boxc. boxlr. boxlc.
/*---------------------------------------------------------------------
* aa.r.c contains the known digits
* we determine which digits are possible for empty positions
* and put them into poss.r.c
*--------------------------------------------------------------------*/

all='123456789'
Parse Value '' With dr. dc. db. /* initialize strings built here */
poss.=''
Do r=1 To 9
Do c=1 To 9
dr.r=dr.r||aa.r.c /* all digits in row r */
End
End
Do c=1 To 9
Do r=1 To 9
dc.c=dc.c||aa.r.c /* all digits in col c */
End
End
Do b=1 To 9
Do r=boxlr.b For 3
Do c=boxlc.b For 3
db.b=db.b||aa.r.c /* all digits in box b */
End
End
End
 
g.0tot=0 /* total # of possible digits */
g.0todo=0 /* number of cells to be filled */
g.0comb=1 /* # of possible combinations */
 
Do r=1 To 9
Do c=1 To 9 /* do this for every r.c */
b=box.r.c /* the box this cell is in */
If aa.r.c='' Then Do /* cell not yet known */
used=compress(dr.r||dc.c||db.b) /* all digits already used */
poss.r.c=diff(all,used) /* all others are still possible */
g.0todo=g.0todo+1 /* number of cells yet to fill */
g.0tot=g.0tot+length(poss.r.c)
g.0comb=g.0comb*length(poss.r.c)
End
End
End
If g.0sol<>'' Then /* if we know the solution */
Call check_all /* check if everything fits */
Return
 
solve:
/*---------------------------------------------------------------------
* Use several algorithms to determine which cell(s) can safely be set
* prunewalt: if a digit occurs just once
* in a row's, col's or box's list of possible digits
* prunesing: if there is only one possible digit in a cell
* pruneexcl ) Algorithms of version 1 only partly understood (by me!)
* prunemats ) but faithfully restructured to avoid many Iterate
* pruneline ) instructions.
*--------------------------------------------------------------------*/

Call build_poss /* re-build the possibles */
Do g.0pass=1 By 1 Until g.0todo=0
Call o g.0fn 'is starting prune pass #' g.0pass
found_pass=0
 
found=prunewalt() /* find any singles ? */
found_pass=found_pass+found
If g.0todo=0 Then Leave
If found>0 Then
Call show_grid 'after prunewalt'
 
found=prunesing() /* find any singles ? */
found_pass=found_pass+found
If g.0todo=0 Then Leave
If found>0 Then
Call show_grid 'after prunesing'
 
found=pruneexcl() /* find any excluives ? */
found_pass=found_pass+found
If g.0todo=0 Then Leave
If found>0 Then
Call show_grid 'after pruneexcl'
 
found=prunemats(2) /* find any matches (len=2) */
found_pass=found_pass+found
If g.0todo=0 Then Leave
If found>0 Then
Call show_grid 'after prunemats'
 
found=pruneline() /* find 2 or more on a line? */
found_pass=found_pass+found
If g.0todo=0 Then Leave
If found>0 Then
Call show_grid 'after pruneline'
 
If found_pass>0 Then Do
Call o found_pass 'hits in g.0pass' g.0pass
If g.0debug Then
Call write_summary
End
Else Do
Call o 'Nothing found in g.0pass' g.0pass
Leave
End
End /* prunes */
Return
 
prunewalt: Call o '>>>>>> prunewalt tot='g.0tot 'todo='g.0todo
/*---------------------------------------------------------------------
* find digits that have only one occurrence in a row or column
* row_poss.r digits in row r
* col_poss.c digits in column c
* box_poss.b digits in box b
*--------------------------------------------------------------------*/

foundwalt=0 /* no matches found so far. */
Do Until changed=0 /* keep searching ... */
changed=0 /* changes made in this routine */
row_poss.='' /* build str for each row */
col_poss.='' /* build str for each column */
box_poss.='' /* build str for each box */
 
Do r=1 To 9
Do c=1 To 9
b=box.r.c
If poss.r.c\=='' Then Do
row_poss.r=row_poss.r poss.r.c
col_poss.c=col_poss.c poss.r.c
box_poss.b=box_poss.b poss.r.c
End
End
End
rl=''
Do r=1 To 9
ol='row'r':'
Do d=1 To 9
cnt=count(d,row_poss.r)
ol=ol cnt
If cnt=1 Then Do
rl=rl r
dr.r=d
End
End
End
cl=''
Do c=1 To 9
ol='col'c':'
Do d=1 To 9
cnt=count(d,col_poss.c)
ol=ol cnt
If cnt=1 Then Do
dc.c=d
cl=cl c
End
End
End
 
bl=''
Do b=1 To 9
ol='box'||b':'
Do d=1 To 9
cnt=count(d,box_poss.b)
ol=ol cnt
If cnt=1 Then Do
z=r'.'c
db.z=d
bl=bl z
End
End
End
 
Do While rl<>''
Parse Var rl r rl
Do c=1 To 9
If pos(dr.r,poss.r.c)>0 Then Do
Call set_aa r,c,dr.r,'prunewalt new R'
changed=changed+1
foundwalt=foundwalt+1
Call build_poss /* re-build the possibles */
End
End
End
Do While cl<>''
Parse Var cl c cl
Do r=1 To 9
If pos(dc.c,poss.r.c)>0 Then Do
Call set_aa r,c,dc.c,'prunewalt new C'
changed=changed+1
foundwalt=foundwalt+1
Call build_poss /* re-build the possibles */
End
End
End
Do While bl<>''
Parse Var bl z cb bl
Parse Var z rb '.' cb
Do r=boxlr.b For 3
Do c=boxlc.b For 3
If r=rb &,
c=cb &,
pos(db.z,poss.r.c)>0 Then Do
Say 'z='r 'c='c 'poss.'r'.'c'='poss.r.c 'db.b='db.b
Call set_aa r,c,db.b,'prunewalt new B'
changed=changed+1
foundwalt=foundwalt+1
Call build_poss /* re-build the possibles */
End
End
End
End
End
Call show_poss 'after prunewalt'
 
If foundwalt>0 Then
Call o '>>>>>> prunewalt foundwalt='foundwalt
Else
Call o '>>>>>> prunewalt found nothing'
g.0foundwalt=g.0foundwalt+foundwalt
Return foundwalt
 
prunesing: Call o '>>>>>> prunesing tot='g.0tot 'todo='g.0todo
/*---------------------------------------------------------------------
* look if there are cells with a single possible digit and put these
* into the grid. Return the number of changes made.
*--------------------------------------------------------------------*/

foundsing=0
Do r=1 To 9
Do c=1 To 9
If length(poss.r.c)=1 Then Do /* only possible digit */
Call set_aa r,c,poss.r.c,'prunesing' /* put it into the cell */
foundsing=foundsing+1 /* indicate success */
End
End
End
If foundsing>0 Then Do
Call build_poss /* re-build the possibles */
Call o '>>>>>> prunesing foundsing='foundsing
End
Else
Call o '>>>>>> prunesing found nothing'
g.0foundsing=g.0foundsing+foundsing
Return foundsing
 
pruneexcl: Call o '>>>>>> pruneexcl tot='g.0tot 'todo='g.0todo
/*---------------------------------------------------------------------
*
*--------------------------------------------------------------------*/

foundexcl=0
Do exclusives=1 /* keep building possibles. */
Do r=1 For 9
Do c=1 For 9
z=poss.r.c
lz=length(z) /* get length of possible. */
If lz>0 Then Do
y=''
b=box.r.c
Do br=boxr.b For 3
Do bc=boxc.b For 3 /* for every cell in box b */
If br'.'bc<>r'.'c Then
y=y||aa.br.bc||poss.br.bc
End
End
Do t=1 For lz
q=substr(z,t,1)
If pos(q,y)==0 Then Do
foundexcl=foundexcl+1
If aa.r.c=q Then
Call o 'pruneexcl ??? aa.'r'.'c'='q 'already set'
Call o 'foundexcl='foundexcl
Call set_aa r,c,q,'pruneexcl' /* a singularity, a sol */
Call o 'pruneexcl found the digit' q,
'by exclusiveness at cell' drc(r,c,z)
Call build_poss /* re-build the possibles */
Iterate exclusives
End
End
End
End
End
Leave
End
If foundexcl>0 Then Do
Call o '>>>>>> pruneexcl foundexcl='foundexcl
End
Else
Call o '>>>>>> prunesing found nothing'
g.0foundexcl=g.0foundexcl+foundexcl
Return foundexcl
 
prunemats: Call o '>>>>>> prunemats tot='g.0tot 'todo='g.0todo
/*---------------------------------------------------------------------
* This example illustrates the working of this strategy:
* Column 1 2 3 4 5 6 7 8 9
* Row 7: . . 1369 29 26 29 137 . 136
* remove 29 from drc 7.3=1369 giving drc 7.3=136 (matches 7.4 7.6)
* Row 7: . . 136 29 26 29 137 . 136
* remove 29 from drc 7.5=26 giving drc 7.5=6 (matches 7.4 7.6) HIT
* Row 7: . . 136 29 6 29 137 . 136
* Row 7: . . 139 29 . 29 137 . 13
* remove 29 from drc 7.3=139 giving drc 7.3=13 (matches 7.4 7.6)
* Row 7: . . 13 29 . 29 137 . 13
* remove 13 from drc 7.7=137 giving drc 7.7=7 (matches 7.9 7.3) HIT
* Row 7: . . 13 29 . 29 7 . 13
* Row 7: . . 139 29 . 29 . . 13
*--------------------------------------------------------------------*/

setmats=0
foundmats=0 /* no matches found so far. */
Parse Arg l /* length of match, L=2,pair */
Do matches=1
Do r=1 For 9
Do c=1 For 9
_=length(poss.r.c) /* get length of possible. */
If _=l Then Do
qq=poss.r.c
m=0 /* count of matches so far. */
mla=r'.'c
Do _c=1 For 9 /* a match in same row? */
If _c<>c &,
qq==poss.r._c Then Do
m=m+1 /* up count if it's a match. */
mla=mla r'.'_c
End
End
If m>0 Then Do
Call o 'AAAA mla='mla
Call show_poss_r r
Do pc=1 For 9 /* remove other possibles. */
old=poss.r.pc /* save the "old" value. */
If old<>qq & old<>'' Then Do
new=diff(old,qq) /* remove mat's digs from X. */
Call o 'AAAA' r'.'pc':'old '-' qq '-->' new
If new<>old Then Do
If length(new)=1 Then tag='HIT'; Else tag=''
Call o 'remove' qq 'from' drc(r,pc,old),
'giving' drc(r,pc,new) '(matches' mla')' tag
poss.r.pc=new /* store new value into old. */
Call show_poss 'AAAA1'
Call show_poss_r r
setmats=setmats+1 /* indicate match was found. */
If length(new)==1 Then Do /*reduce if L=1*/
Call set_aa r,pc,new,'prunemats R' /*store single*/
foundmats=foundmats+1 /* indicate match was found*/
Call build_poss /* re-build the possibles */
Call show_poss 'AAAA2'
Call show_poss_r r
Iterate matches /* start over. */
End
End
End
End
End
m=0
mlb=r'.'c
Do _r=1 For 9
If _r<>r &,
qq==poss._r.c Then Do
m=m+1
mlb=_r'.'c
End
End
 
If m>0 Then Do
Call o 'BBBB mlb='mlb
Call show_poss_r r
Do pr=1 For 9
old=poss.pr.c
If old<>qq & old<>'' Then Do
new=diff(old,qq)
Call o 'BBBB' pr'.'c':'old '-' qq '-->' new
If new<>old Then Do
If length(new)=1 Then tag='HIT'; Else tag=''
Call o 'remove' qq 'from' drc(pr,c,old),
'giving' drc(pr,c,new) '(matches' mlb')' tag
poss.pr.c=new
Call show_poss_r r
Call show_poss 'BBBB1'
setmats=setmats+1
If length(new)==1 Then Do
foundmats=foundmats+1
Call set_aa pr,c,new,'prunemats C'
Call build_poss /* re-build the possibles */
Call show_poss 'BBBB2'
Call show_poss_r r
Iterate matches
End
End
End
End
End
End
End
End
Leave
End
 
If foundmats>0 Then Do
Call o '>>>>>> prunemats foundmats='foundmats
End
Else
Call o '>>>>>> prunesing found nothing'
g.0foundmats=g.0foundmats+foundmats
Return setmats
 
pruneline: Call o '>>>>>> pruneline tot='g.0tot 'todo='g.0todo
/*---------------------------------------------------------------------
*
*--------------------------------------------------------------------*/

Call show_poss ' vor pruneline'
pruned=0
foundline=0 /* no matches found so far. */
Do Until changes=0 /* terminate if no changes made */
changes=0 /* initialize number of changes */
poss_boxr.='' /* build str for each boxrow */
poss_boxc.='' /* build str for each boxcol */
Do r=1 To 9
Do c=1 To 9
b=box.r.c
If poss.r.c\=='' Then Do
poss_boxr.r.b=strip(poss_boxr.r.b poss.r.c)
poss_boxc.c.b=strip(poss_boxc.c.b poss.r.c)
End
End
End
Do r=1 To 9 /* search all rows for twins */
Do cb=1 To 7 By 3 /* 3 boxes containing row r */
b=box.r.cb
aline=poss_boxr.r.b /* all poss strings: row r box b */
If words(aline)>=2 Then Do /* more than one */
Call o 'aline' r'.'||b'='aline '(cb='cb')'
Do k=1 To 9 /* search for each digit. */
If count(k,aline)>=2 Then Do /* more than one occurrence */
Do jr=rowlb.r For 3 /* look at the other 2 rows. */
If jr<>r &,
pos(k,poss_boxr.jr.b)>0 Then /* digit k found */
Iterate k /* continue with the next digit */
End
Do jb=rowlb.r For 3 /* search boxes of row R for K. */
If jb<>b &,
pos(k,poss_boxr.r.jb)>0 Then Do
Do kc=1 To 9 /* find which cell K is in. */
If box.r.kc<>b Then Do
If poss.r.kc<>'' &,
pos(k,poss.r.kc)>0 Then Do
old=drc(r,kc,poss.r.kc)
row_a=poss_r(r)
poss.r.kc=diff(poss.r.kc,k) /* remove digit k*/
Call o g.0fn 'row' r': removing' k 'from' old,
'resulting in' drc(r,kc,poss.r.kc)
row_b=poss_r(r)
Call o ' ' row_a
Call o '>>' row_b
pruned=pruned+1
If length(poss.r.kc)==1 Then Do
Call set_aa r,kc,poss.r.kc,'pruneline R'
foundline=foundline+1
Call build_poss /* re-build the possibles */
changes=changes+1
End
End
End
End
End
End
End
End
End
End
End
 
Do c=1 To 9 /* search all cols for twins */
Do b=collb.c By 3 For 3 /* for each col, search box. */
aline=poss_boxc.c.b
If words(aline)>=2 Then Do
Do k=1 To 9 /* search for each digit. */
If count(k,aline)>=2 Then Do
Do jc=boxlc.b For 3 /* look at the other 2 cols. */
If jc<>c&pos(k,poss_boxc.jc.b)<>0 Then
Iterate k /* if no digit K, ignore */
End /* jc */
/*found 2 Ks in col C box B */
Do jb=collb.c By 3 For 3 /*search boxes col C for K. */
If jb<>b&pos(k,poss_boxc.c.jb)<>0 Then Do
Do kr=1 To 9 /* find which cell K is in. */
If box.kr.c<>b Then Do
If poss.kr.c>''&,
pos(k,poss.kr.c)>0 Then Do
old=drc(kr,c,poss.kr.c)
col_a=poss_c(c)
poss.kr.c=diff(poss.kr.c,k) /* remove digit k*/
Call o g.0fn 'col' c': removing' k 'from' old,
'resulting in' drc(kr,c,poss.kr.c)
col_b=poss_c(c)
Call o ' ' col_a
Call o '>>' col_b
pruned=pruned+1
If length(poss.kr.c)==1 Then Do
Call set_aa kr,c,poss.kr.c,'pruneline C'
foundline=foundline+1
Call build_poss /* re-build the possibles */
changes=changes+1
End
End
End
End
End
End
End
End
End
End
End
End
Call show_poss 'nach pruneline'
If foundline>0 Then
Call o '>>>>>> pruneline new foundline='foundline 'pruned='pruned
Else
Call o '>>>>>> pruneline new found nothing' 'pruned='pruned
g.0foundline=g.0foundline+foundline
Return foundline
 
show_grid:
/*---------------------------------------------------------------------
* show what's known so far
* and what's still to be done
*--------------------------------------------------------------------*/

Parse Arg title
Call show_aa title
Call show_poss title
Return
 
show_aa: Procedure Expose g. aa. s.
/*---------------------------------------------------------------------
* Show all cells that are known already
* and determine the number of cells yet to be filled (g.0todo)
*--------------------------------------------------------------------*/

Parse Arg txt
blank='.'
Select
When txt='the puzzle' |, /* initial call */
txt='solved' Then /* final call (success) */
g.0say=1 /* show on screen */
When txt='failed' Then Do /* final call (failure) */
g.0say=1 /* show on screen */
g.0fail=1 /* write to incomplete solution */
End
Otherwise
g.0say=0 /* don't show on screen */
End
Call o txt /* write to dbg/screen/inco */
g.0todo=0
Do r=1 To 9 /* for all rows */
ol=''
Do c=1 To 9 /* build a line */
If aa.r.c='' Then Do
g.0todo=g.0todo+1
ol=ol blank
End
Else
ol=ol aa.r.c
If c//3=0 Then /* a blank column */
ol=ol' '
End
Call o ol
If r//3=0 Then /* a blank line */
Call o ' '
End
g.0say=0 /* reset the flags */
g.0fail=0
If g.0todo>0 Then
Call o right('to be done:',40) g.0todo
Else
Call o 'all done'
Return
 
show_poss: Procedure Expose poss. g. s.
/*---------------------------------------------------------------------
* show all possible digits of the grid
*--------------------------------------------------------------------*/

Parse Arg txt
If g.0todo=0 Then
Return
Call o copies('-',70) 'todo='g.0todo
Call o txt
Do r=1 To 9
ol=r
Do c=1 To 9
ol=ol left(poss.r.c,7)
If c//3=0 Then
ol=ol '|'
End
Call o ol
If r//3=0 Then
Call o ' '
End
Call o ' tot='g.0tot 'todo='g.0todo
Call o 'combinations:' g.0comb
Return
 
show_poss_r: Procedure Expose g. poss.
/*---------------------------------------------------------------------
* show possible digits in row r
'--------------------------------------------------------------------*/

Parse Arg r
Call o poss_r(r)
Return
 
poss_r: Procedure Expose g. poss.
/*---------------------------------------------------------------------
* compute possible digits in row r
'--------------------------------------------------------------------*/

Parse Arg r
ol='Row' r':'
Do c=1 To 9
prc=poss.r.c
If prc='' Then prc='.'
ol=ol left(prc,6)
End
Return ol
 
show_poss_c: Procedure Expose g. poss.
/*---------------------------------------------------------------------
* show possible digits in column c
'--------------------------------------------------------------------*/

Parse Arg c
Call o poss_c(c)
Return
 
poss_c: Procedure Expose g. poss.
/*---------------------------------------------------------------------
* compute possible digits in column c
'--------------------------------------------------------------------*/

Parse Arg c
ol='Col' c':'
Do r=1 To 9
prc=poss.r.c
If prc='' Then prc='.'
ol=ol left(prc,6)
End
Return ol
 
compress: Procedure
/*---------------------------------------------------------------------
* build a string containing the digits found in s
* Example: compress('11 9 33 55') -> '1359'
*--------------------------------------------------------------------*/

Parse Arg s
res=''
Do d=1 To 9
If pos(d,s)>0 Then
res=res||d
End
Return left(res,9)
 
diff:
/*---------------------------------------------------------------------
* build the 'difference' of two strings (same as squish in version 1)
* Return a string of digits contained in arg(1) not existant in arg(2)
* Example: diff('13895','35') -> '189'
*--------------------------------------------------------------------*/

Return space(translate(arg(1),,word(arg(2) ',',1)),0)
 
check_all:
/*---------------------------------------------------------------------
* check the current status against the target (if this is known)
*--------------------------------------------------------------------*/

error=0
Do r=1 To 9
Do c=1 To 9
If aa.r.c=''|aa.r.c=s.r.c Then
Nop
Else Do
Call o 'r='r 'c='c 'soll='s.r.c 'ist='aa.r.c
error=1
End
End
End
Do r=1 To 9
Do c=1 To 9
Select
When poss.r.c='' Then
Nop
When pos(s.r.c,poss.r.c)>0 Then
Nop
Otherwise Do
Call o 'r='r 'c='c aa.r.c 'not in poss:'poss.r.c
error=1
End
End
End
End
If error Then
Call exit 'an error in check_all'
Return
 
o:
/*---------------------------------------------------------------------
* write to the debug file (when g.0debug is true)
* and, if applicable, to the screen (when g.0say is true)
* and to the incomplete solution (when g.0fail is true)
*--------------------------------------------------------------------*/

If g.0say Then
Say arg(1)
If g.0fail Then
Call lineout g.0inco,arg(1)
If g.0debug Then
Call lineout g.0dbg,arg(1)
Return
 
set_aa: Procedure Expose g. aa. poss. box. boxr. boxc. boxlr. boxlc.,
s. sigl
/*---------------------------------------------------------------------
* put a digit into the cell r.c and show the text given
*--------------------------------------------------------------------*/

Parse Arg r,c,d,text
from=sigl
If s.r.c<>'*' &,
d<>s.r.c Then Do
call o 'Trying t set aa.'r'.'c 'to' d 'but should be' s.r.c
Call o 'from='from
Exit
End
 
Call o 'setting aa.'r'.'c' to d='d '('text')'
If g.0done.r.c=1 Then Do
Call o 'cell' r'.'c'='aa.r.c '>' d '?????' 'called_from='sigl,
'in pass' g.0pass
End
aa.r.c=d /* put the digit into the cell */
poss.r.c='' /* remove cell's possible digits */
g.0done.r.c=1 /* note that cell was set */
Return
 
count: Procedure
/*---------------------------------------------------------------------
* Return the number of occurrences of d in s (all digits)
* Example: count(3,'123 567 399 13') -> 3
*--------------------------------------------------------------------*/

Parse Arg d,s
s=translate(s,'*',d)
s=translate(s,'','123456789')
s=space(s,0)
Return length(s)
 
drc: Procedure
/*---------------------------------------------------------------------
* return coordinates and contents of a cell as r.c=string
*--------------------------------------------------------------------*/

Parse Arg r,c,s
Return 'drc' r'.'c'='s
 
set_geometry:
/*---------------------------------------------------------------------
* set miscellaneous relations and limits
*--------------------------------------------------------------------*/

box.=''
Do b=1 For 9 /* build the box bounds. */
rr=(((b*3)%10)+1)*3-2 /* compute row lower bound. */
cc=(((b-1)//3)+1)*3-2 /* compute col lower bound. */
boxr.b=rr
boxc.b=cc
Do r=rr To rr+2 /* build boxes with cell #s. */
Do c=cc To cc+2
rc=r||c
box.b=box.b rc
box.r.c=b
End
End
box.b=strip(box.b)
End
 
rowlb.=9 /* row R, low box number=b. */
collb.=9 /* col R, low box number=b. */
boxlr.=9 /* box B, low row number=r. */
boxlc.=9 /* box B, low col number=c. */
Do r=1 To 9
Do c=1 To 9
b=box.r.c /* what box is this R,C in ? */
rowlb.r=min(rowlb.r,b) /* find min box # for row R. */
collb.c=min(collb.c,b) /* find min box # for col C. */
boxlr.b=min(boxlr.b,r) /* find min row # for box B. */
boxlc.b=min(boxlc.b,c) /* find min col # for box B. */
End /* c */
End /* r */
Return
 
get_input: Procedure Expose g. aa. s.
/*---------------------------------------------------------------------
* get the given puzzle
* 9 rows with 9 columns each containing a digit or a place holder (.x0)
* set the miscellaneous file-ids
* and get the known solution (if available) for checking in get_sol
*--------------------------------------------------------------------*/

Parse Arg g.0fid
Parse Var g.0fid g.0fn '.'
If g.0debug Then Do
g.0dbg=g.0fn'.dbg' /* file to contain debug output */
/*********************************
Call lineout g.0dbg
If lines(g.0dbg)>0 Then /* if the file exists */

'erase' g.0dbg /* erase it */
*********************************/
End
If pos('.',g.0fid)=0 Then
g.0fid=g.0fid'.in'
digits='123456789'
g.0fidx=g.0fid
Say 'process file' g.0fidx
If lines(g.0fidx)=0 Then
Call exit 'Input file does not exist'
instr=''
Do While lines(g.0fidx)>0
instr=instr linein(g.0fidx)
End
Call lineout g.0fidx
instr=translate(instr,digits'000',digits'.x0'||xrange('00'x,'ff'x))
instr=space(instr,0)
Select
When length(instr)<81 Then Do
Say 'instr='instr'<'
Call exit 'Incorrect input - not enough data'
End
When length(instr)>81 Then Do
Say 'instr='instr'<'
Call exit 'Incorrect input - too much data'
End
Otherwise Do
Call o ' instr='instr'<'
instr=translate(instr,' ','0')
End
End
Do r=1 To 9
Do c=1 To 9
Parse Var instr aa.r.c +1 instr
End
End
g.0inco=g.0fn'f.in' /* file to contain failed res */
if lines(g.0inco)>0 Then /* if the file exists */
'erase' g.0inco /* erase it */
g.0summ='sudoku.summary' /* file to get statistics */
g.0sol= 'sol\'g.0fn'.sol' /* known solution for checking */
If lines(g.0sol)>0 Then /* if that file is found */
Call get_sol /* get its data */
Else Do /* otherwise */
g.0sol='' /* don't check */
s.='*'
End
Say 'Input from ' g.0fidx
Say 'Debug output to ' g.0dbg
If lines(g.0sol)>0 Then /* if that file is found */
Say 'Given solution from' g.0sol
Say 'Statistics to ' g.0summ
Say 'Incomplete solution' g.0inco '(if applicable)'
Say 'Hit enter to proceed'
Return
 
get_sol: Procedure Expose g. s.
/*---------------------------------------------------------------------
* get the known solution
* (9 rows with 9 columns each containing a digit)
*--------------------------------------------------------------------*/

solvstr=''
If lines(g.0sol)>0 Then Do
Do While lines(g.0sol)>0
solvstr=solvstr linein(g.0sol)
End
Call lineout g.0sol
solvstr=space(solvstr,0)
Call o 'solution='solvstr
Do r=1 To 9
Do c=1 To 9
Parse Var solvstr s.r.c +1 solvstr
End
End
Do r=1 To 9
ol=s.r.1
Do c=2 To 9
ol=ol s.r.c
If c//3=0 Then ol=ol' '
End
Call o ol
If r//3=0 Then
Call o ' '
End
End
Return
 
exit: Say 'EXIT' arg(1)
Exit
 
write_summary: Procedure Expose g.
/*---------------------------------------------------------------------
* add a line to the statistics
* file init walt sing excl mats line todo pass
* sdk002.in 56 56 0 0 0 0 0 1
* sdk007.in 61 16 0 0 1 5 39 1 <---
* sdk007.in 61 55 0 0 1 5 0 2 solved
* sdk088.in 50 14 2 34 0 0 0 1
* sdk093.in 55 2 2 1 0 0 50 2 <---
* sdk093.in 55 2 2 1 0 0 50 2 <--- no success
*--------------------------------------------------------------------*/

If lines(g.0summ)=0 Then /* write header line */
Call lineout g.0summ,,
'file init walt sing excl mats line todo pass'
If g.0todo>0 Then tag='<---' /* mark a failure */
Else tag=''
/* show # of hits for each strategy */
summline=left(g.0fid,10) right(g.0todo_init,4),
right(g.0foundwalt,4),
right(g.0foundsing,4),
right(g.0foundexcl,4),
right(g.0foundline,4),
right(g.0foundmats,4),
right(g.0todo,4),
right(g.0pass,4) tag
/*
Say summline
*/

Call lineout g.0summ,summline
Call lineout g.0summ /* close the file */
Return
 
novalue:
Say 'Novalue raised in line' sigl
Say sourceline(sigl)
Say 'Variable' condition('D')
Signal lookaround
 
syntax:
Say 'Syntax raised in line' sigl
Say sourceline(sigl)
Say 'rc='rc '('errortext(rc)')'
 
halt:
lookaround:
If fore() Then Do
Say 'You can look around now.'
Trace ?R
Nop
End
Exit 12
Output:
process file sdk087.in
Input from          sdk087.in
Debug output to     0
Given solution from
Statistics to       sudoku.summary
Incomplete solution sdk087f.in (if applicable)
Hit enter to proceed
the puzzle
 . . .  . . .  3 . .
 . . .  . 7 1  5 . .
 . . 2  4 . 6  . 1 8

 . . .  . . 9  . 4 6
 . 9 .  6 1 8  . 3 .
 6 1 .  7 . .  . . 9

 4 3 .  8 . 7  6 . .
 . . 8  1 4 .  . . .
 . . 9  . . .  . . .

solved
 7 4 1  9 8 5  3 6 2
 3 8 6  2 7 1  5 9 4
 9 5 2  4 3 6  7 1 8

 8 2 7  3 5 9  1 4 6
 5 9 4  6 1 8  2 3 7
 6 1 3  7 2 4  8 5 9

 4 3 5  8 9 7  6 2 1
 2 6 8  1 4 3  9 7 5
 1 7 9  5 6 2  4 8 3