1 REM SUDOKU SOLVER V 1.0 BY GRAHAM DEARSLEY
5 REM SETUP DISPLAY AND HIDE SYSTEM CURSOR
10 GRAPHICS 0:SETCOLOR 2,0,0:POKE 752,1
20 GOSUB 5000
30 GOSUB 6000
40 CX=30:CY=6:REM CURSOR POSITION
50 COX=30:COY=6:REM OLD CURSOR POSITION
60 CCOLD=49:REM OLD CURSOR CONTENT
70 BLATCH=1:REM BUTTON LATCH
80 DIM SUDOKU(9,9):REM DIMENSION MATRIX ARRAY
90 DIM TEMP$(9):TEMP$=""
100 GOSUB 8000
495 REM MAIN LOOP
500 J=STICK(0):T=STRIG(0)
510 IF J=7 THEN GOSUB 7000:REM RIGHT
520 IF J=11 THEN GOSUB 7100:REM LEFT
530 IF J=14 THEN GOSUB 7200:REM UP
540 IF J=13 THEN GOSUB 7300:REM DOWN
550 IF T=0 THEN GOSUB 7400:REM TRIGER BUTTON
560 POKE 77,0:REM RESET SCREEN SAVER TIMER
570 GOTO 500
4990 END 
4995 REM PLOT THE GRID
5000 POSITION 2,0
5010 PRINT "   "
5020 FOR I=1 TO 2
5030 PRINT " | | |   | |   | | |"
5040 PRINT " 
  "
5050 PRINT " | | |   | |   | | |"
5060 PRINT " 
  "
5070 PRINT " | | |   | |   | | |"
5080 PRINT "                    "
5090 NEXT I
5100 PRINT " | | |   | |   | | |"
5110 PRINT " 
  "
5120 PRINT " | | |   | |   | | |"
5130 PRINT " 
  "
5140 PRINT " | | |   | |   | | |"
5150 PRINT "   "
5160 RETURN 
5995 REM PLOT THE NUM PAD
6000 POSITION 30,6:PRINT "1 2 3"
6010 POSITION 30,8:PRINT "4 5 6"
6020 POSITION 30,10:PRINT "7 8 9"
6030 POSITION 30,12:PRINT "SOLVE"
6040 RETURN 
6995 REM CONDITION BLOCK
7000 CX=CX+2
7010 IF CX>34 THEN CX=CX-2:RETURN 
7015 IF CX>22 AND CY=12 THEN CX=CX-2:RETURN 
7020 IF CX=22 THEN POSITION COX,COY:PRINT CHR$(CCOLD):CX=30:CY=6:COX=30:COY=6:CCOLD=49
7070 IF CX<22 THEN BLATCH=1:GOSUB 9000
7080 IF CX>22 THEN GOSUB 8000
7090 RETURN 
7100 CX=CX-2
7110 IF CX<3 THEN CX=CX+2:RETURN 
7115 IF CX>22 AND CY=12 THEN CX=CX+2:RETURN 
7120 IF CX=28 THEN CX=CX+2:RETURN 
7170 IF CX<22 THEN BLATCH=1:GOSUB 9000
7180 IF CX>22 THEN GOSUB 8000
7190 RETURN 
7200 CY=CY-2
7210 IF CY<0 THEN CY=CY+2:RETURN 
7215 IF CX>20 AND CY=10 THEN POSITION 30,12:PRINT "SOLVE"
7220 IF CX>20 AND CY<6 THEN CY=CY+2:RETURN 
7270 IF CX<22 THEN BLATCH=1:GOSUB 9000
7280 IF CX>22 THEN GOSUB 8000
7290 RETURN 
7300 CY=CY+2
7310 IF CY>18 THEN CY=CY-2:RETURN 
7320 IF CX>20 AND CY>12 THEN CY=CY-2:RETURN 
7370 IF CX<22 THEN BLATCH=1:GOSUB 9000
7380 IF CX>22 THEN GOSUB 8000
7385 IF CX>20 AND CY=12 THEN POSITION 30,12:PRINT "ΣΟΜΦΕ"
7390 RETURN 
7400 IF CX<22 AND BLATCH=1 THEN CCOLD=CCONTENT:GOSUB 9000
7410 IF CX<22 AND BLATCH=-1 THEN CCOLD=32:GOSUB 9000
7415 IF CX>20 AND CY<12 THEN BLATCH=-1
7420 IF CX>20 AND CY<12 THEN POSITION COX,COY:PRINT CHR$(CCOLD):LOCATE 4,1,CCOLD:CX=4:CY=1:COX=4:COY=1:GOSUB 9000
7430 IF CX<22 THEN BLATCH=-BLATCH
7440 IF CX>20 AND CY=12 THEN GOSUB 10000
7490 RETURN 
7995 REM PLOT NUM PAD CURSOR
8000 LOCATE CX,CY,CCONTENT
8010 POSITION COX,COY:PRINT CHR$(CCOLD)
8020 CCOLD=CCONTENT
8030 POSITION CX,CY:PRINT CHR$(CCONTENT+128)
8040 COX=CX:COY=CY
8050 SOUND 0,255,10,10
8060 FOR DELAY=1 TO 20:NEXT DELAY
8070 SOUND 0,0,0,0
8080 RETURN 
8995 REM PLOT GRID CURSOR
9000 POSITION COX,COY:PRINT CHR$(CCOLD)
9010 LOCATE CX,CY,CCOLD
9020 POSITION CX,CY:PRINT CHR$(CCONTENT+128)
9030 COX=CX:COY=CY
9040 SOUND 0,255,10,10
9050 FOR DELAY=1 TO 20:NEXT DELAY
9060 SOUND 0,0,0,0
9070 RETURN 
9995 REM FILL SUDOKU MATRIX
10000 POSITION 29,1:PRINT "WORKING"
10005 POSITION 5,21:PRINT "         "
10010 FOR COL=0 TO 8
10020 FOR ROW=0 TO 8
10025 POSITION 1,21:PRINT COL:POSITION 1,22:PRINT ROW
10030 LOCATE (COL*2)+4,(ROW*2)+1,VALUE:POSITION (COL*2)+4,(ROW*2)+1:PRINT CHR$(VALUE)
10040 SUDOKU(COL,ROW)=VALUE-48
10050 NEXT ROW
10060 NEXT COL
10070 POSITION 28,1:PRINT "          "
10195 REM THE LOGIC  ! ! !
10196 PASS=1
10197 FILLED=0
10198 POSITION 23,3:PRINT "PASS ";PASS
10200 FOR ROW=0 TO 8:REM PROCESS THE ROWS
10210 POSCOL=0:POSROW=0:POSNUM=0
10220 GOSUB 10500:REM PUT UNFILLED NUMBERS FOR ROW IN TEMP$
10230 FOR CHECK=1 TO LEN(TEMP$)
10232 COUNT=0
10235 FOR COL=0 TO 8
10237 IF COUNT>1 THEN GOTO 10250
10240 GOSUB 10710:REM CHECK NUMBER IS UNIQUE IN COLUNM
10243 POSITION 20,20:PRINT "TRUE ";TRUE:POSITION 27,20:PRINT "COUNT ";COUNT
10245 POSITION 20,21:PRINT "POSROW ";POSROW:POSITION 29,21:PRINT "POSCOL ";POSCOL
10247 POSITION 20,22:PRINT "POSNUM ";POSNUM
10250 NEXT COL
10350 IF COUNT=1 THEN SUDOKU(POSCOL,POSROW)=POSNUM:FILLED=FILLED+1
10355 IF COUNT=1 THEN POSITION (POSCOL*2)+4,(POSROW*2)+1:PRINT POSNUM
10360 NEXT CHECK
10390 TEMP$=""
10400 NEXT ROW
10401 GOSUB 11200
10402 IF FILLED>0 THEN PASS=PASS+1:GOTO 10197
10405 POSITION 23,1:PRINT "                "
10410 RETURN :REM RETURN TO MAIN PROGRAM
10495 REM FILL TEMP$
10500 POSITION 23,1:PRINT "PROCESSING ROW ";ROW+1
10510 FOR NUMBER=1 TO 9
10520 MARK=1
10530 FOR COL=0 TO 8
10550 IF SUDOKU(COL,ROW)=NUMBER THEN MARK=0
10560 NEXT COL
10570 IF MARK=1 THEN TEMP$(LEN(TEMP$)+1)=STR$(NUMBER)
10580 NEXT NUMBER
10590 POSITION 5,21:PRINT "          "
10600 POSITION 5,21:PRINT TEMP$
10610 RETURN :REM RETURN TO 10220
10710 REM 
10720 IF SUDOKU(COL,ROW)<>-16 THEN RETURN 
10725 TRUE=1
10730 FOR ROWTAG=0 TO 8
10740 IF SUDOKU(COL,ROWTAG)=VAL(TEMP$(CHECK,CHECK)) THEN TRUE=0
10750 NEXT ROWTAG
10752 IF TRUE=1 THEN GOSUB 12000
10755 IF TRUE=1 AND COUNT>0 THEN COUNT=COUNT+1
10760 IF TRUE=1 AND COUNT=0 THEN POSCOL=COL:POSROW=ROW:POSNUM=VAL(TEMP$(CHECK,CHECK)):COUNT=COUNT+1
10780 RETURN 
11200 FOR COL=0 TO 8:REM PROCESS THE COLUNMS
11210 POSCOL=0:POSROW=0:POSNUM=0
11220 GOSUB 11500:REM PUT UNFILLED NUMBERS FOR COLUNM IN TEMP$
11230 FOR CHECK=1 TO LEN(TEMP$)
11232 COUNT=0
11235 FOR ROW=0 TO 8
11237 IF COUNT>1 THEN GOTO 11250
11240 GOSUB 11710:REM CHECK NUMBER IS UNIQUE IN ROW
11243 POSITION 20,20:PRINT "TRUE ";TRUE:POSITION 27,20:PRINT "COUNT ";COUNT
11245 POSITION 20,21:PRINT "POSROW ";POSROW:POSITION 29,21:PRINT "POSCOL ";POSCOL
11247 POSITION 20,22:PRINT "POSNUM ";POSNUM
11250 NEXT ROW
11350 IF COUNT=1 THEN SUDOKU(POSCOL,POSROW)=POSNUM:FILLED=FILLED+1
11355 IF COUNT=1 THEN POSITION (POSCOL*2)+4,(POSROW*2)+1:PRINT POSNUM
11360 NEXT CHECK
11390 TEMP$=""
11400 NEXT COL
11402 RETURN 
11405 POSITION 23,1:PRINT "                "
11410 RETURN :REM RETURN TO MAIN PROGRAM
11495 REM FILL TEMP$
11500 POSITION 23,1:PRINT "PROCESSING COL ";COL+1
11510 FOR NUMBER=1 TO 9
11520 MARK=1
11530 FOR ROW=0 TO 8
11550 IF SUDOKU(COL,ROW)=NUMBER THEN MARK=0
11560 NEXT ROW
11570 IF MARK=1 THEN TEMP$(LEN(TEMP$)+1)=STR$(NUMBER)
11580 NEXT NUMBER
11590 POSITION 5,21:PRINT "          "
11600 POSITION 5,21:PRINT TEMP$
11610 RETURN :REM RETURN TO 11220
11710 REM 
11720 IF SUDOKU(COL,ROW)<>-16 THEN RETURN 
11725 TRUE=1
11730 FOR COLTAG=0 TO 8
11740 IF SUDOKU(COLTAG,ROW)=VAL(TEMP$(CHECK,CHECK)) THEN TRUE=0
11750 NEXT COLTAG
11752 IF TRUE=1 THEN GOSUB 12000
11755 IF TRUE=1 AND COUNT>0 THEN COUNT=COUNT+1
11760 IF TRUE=1 AND COUNT=0 THEN POSCOL=COL:POSROW=ROW:POSNUM=VAL(TEMP$(CHECK,CHECK)):COUNT=COUNT+1
11780 RETURN 
12000 IF COL<3 THEN SQCOL=0
12002 IF COL>2 AND COL<6 THEN SQCOL=3
12004 IF COL>5 THEN SQCOL=6
12010 IF ROW<3 THEN SQROW=0
12012 IF ROW>2 AND ROW<6 THEN SQROW=3
12014 IF ROW>5 THEN SQROW=6
12020 FOR SQUARECOL=SQCOL TO SQCOL+2
12030 FOR SQUAREROW=SQROW TO SQROW+2
12040 IF SUDOKU(SQUARECOL,SQUAREROW)=VAL(TEMP$(CHECK,CHECK)) THEN TRUE=0
12050 NEXT SQUAREROW
12060 NEXT SQUARECOL
12070 RETURN