120 lines
3.5 KiB
QBasic
120 lines
3.5 KiB
QBasic
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1 rem Tic Tac Toe solving app that learns what WOPR learned: you can't win
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2 rem Only three starting positions are examined. Others are just reflections of these
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3 rem b% -- The board
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4 rem al% -- Alpha, for pruning
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5 rem be% -- Beta, for pruning
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6 rem l% -- Top-level loop iteration
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7 rem wi% -- The winning piece (0 none, 1 X, 2, O )
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8 rem re% -- Resulting score of 4000/minmax board position. 5 draw, 6 X win, 4 Y win
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9 rem sx% -- Stack array for "recursion" X can be P, V, A, or B for those variables.
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10 rem v% -- Value of a board position
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11 rem st% -- Stack Pointer. Even for alpha/beta pruning Minimize plys, Odd for Maximize
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12 rem p% -- Current position where a new piece is played
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14 rem rw% -- Row in the Winner function (2000)
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15 rem cw% -- Column in the Winner function (2000)
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18 rem mc% -- Move count total for debugging. Should be a multiple of 6493
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19 rem Note: Can't use real recursion with GOSUB because stack is limited to roughly 5 deep
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20 rem BASIC doesn't support goto/gosub using arrays for target line numbers
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21 print "date: "; date$
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30 dim b%(9)
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32 dim sp%(10)
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34 dim sv%(10)
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36 dim sa%(10)
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37 dim sb%(10)
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38 mc% = 0
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39 print "start time: "; time$
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40 for l% = 1 to 10
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41 mc% = 0
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42 al% = 2
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43 be% = 9
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44 b%(0) = 1
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45 gosub 4000
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58 al% = 2
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59 be% = 9
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60 b%(0) = 0
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61 b%(1) = 1
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62 gosub 4000
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68 al% = 2
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69 be% = 9
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70 b%(1) = 0
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71 b%(4) = 1
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72 gosub 4000
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73 b%(4) = 0
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74 rem print "mc: "; mc%; " l is "; l%
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80 next l%
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85 print elap$ ; " for "; l% - 1; " iterations"
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86 print "end time: "; time$
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87 print "final move count "; mc%
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90 system
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100 end
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2000 wi% = b%( 0 )
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2010 if 0 = wi% goto 2100
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2020 if wi% = b%( 1 ) and wi% = b%( 2 ) then return
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2030 if wi% = b%( 3 ) and wi% = b%( 6 ) then return
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2100 wi% = b%( 3 )
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2110 if 0 = wi% goto 2200
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2120 if wi% = b%( 4 ) and wi% = b%( 5 ) then return
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2200 wi% = b%( 6 )
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2210 if 0 = wi% goto 2300
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2220 if wi% = b%( 7 ) and wi% = b%( 8 ) then return
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2300 wi% = b%( 1 )
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2310 if 0 = wi% goto 2400
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2320 if wi% = b%( 4 ) and wi% = b%( 7 ) then return
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2400 wi% = b%( 2 )
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2410 if 0 = wi% goto 2500
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2420 if wi% = b%( 5 ) and wi% = b%( 8 ) then return
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2500 wi% = b%( 4 )
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2510 if 0 = wi% then return
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2520 if wi% = b%( 0 ) and wi% = b%( 8 ) then return
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2530 if wi% = b%( 2 ) and wi% = b%( 6 ) then return
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2540 wi% = 0
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2550 return
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4000 rem minmax function to find score of a board position
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4010 rem recursion is simulated with gotos
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4030 st% = 0
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4040 v% = 0
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4060 re% = 0
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4100 mc% = mc% + 1
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4102 rem gosub 3000
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4104 if st% < 4 then goto 4150
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4105 gosub 2000
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4106 if 0 = wi% then goto 4140
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4110 if wi% = 1 then re% = 6: goto 4280
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4115 re% = 4
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4116 goto 4280
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4140 if st% = 8 then re% = 5: goto 4280
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4150 if st% and 1 then v% = 2 else v% = 9
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4160 p% = 0
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4180 if 0 <> b%(p%) then goto 4500
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4200 if st% and 1 then b%(p%) = 1 else b%(p%) = 2
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4210 sp%(st%) = p%
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4230 sv%(st%) = v%
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4245 sa%(st%) = al%
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4246 sb%(st%) = be%
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4260 st% = st% + 1
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4270 goto 4100
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4280 st% = st% - 1
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4290 p% = sp%(st%)
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4310 v% = sv%(st%)
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4325 al% = sa%(st%)
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4326 be% = sb%(st%)
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4328 b%(p%) = 0
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4330 if st% and 1 then goto 4340
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4331 if re% = 4 then goto 4530
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4332 if re% < v% then v% = re%
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4334 if v% < be% then be% = v%
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4336 if be% <= al% then goto 4520
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4338 goto 4500
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4340 if re% = 6 then goto 4530
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4341 if re% > v% then v% = re%
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4342 if v% > al% then al% = v%
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4344 if al% >= be% then goto 4520
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4500 p% = p% + 1
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4505 if p% < 9 then goto 4180
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4520 re% = v%
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4530 if st% = 0 then return
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4540 goto 4280
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