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148 lines
3.9 KiB
QBasic
148 lines
3.9 KiB
QBasic
REM Advent of Code 2022: Day 5, part 2
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REM Written in Applesoft BASIC
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REM ST$ is our array of nine strings to track the stacked boxes.
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10 DIM ST$(9)
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20 FOR I = 0 TO 8:ST$(I) = "": NEXT I
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REM Clear screen, set error GOTO for end-of-file, and open the input file.
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30 HOME
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40 ONERR GOTO 900
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60 PRINT CHR$ (4),"OPEN INPUT"
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70 PRINT CHR$ (4),"READ INPUT"
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REM J is a byte counter for reading fields (explained below).
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REM K tracks the current stack for building the initial configuration.
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REM L is the current index in AC.
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REM AC is the "action": move AC(0) from AC(1) to AC(2).
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REM V is used to build the values stored in AC.
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90 J = 1
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91 K = 0
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92 L = 0
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93 DIM AC(3):AC(0) = 0:AC(1) = 0:AC(2) = 0
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94 V = 0
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REM Here, we read in the initial stack configuration.
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REM Reminder, GET Z$ scraps bytes that are an artifact to input file xfer.
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REM J tracks where the next stack value is. Stack values are three bytes
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REM apart, either "] [" or "]\n[". We loop through ST$ as we read stack
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REM values, and add to the current stack if we have a letter and not a space.
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REM
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REM Once a digit is encountered, we know that we have finished reading the
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REM initial data.
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100 GET C$: GET Z$
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110 CV = ASC (C$)
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120 IF CV > 47 AND CV < 58 GOTO 300
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130 IF J > 0 THEN J = J - 1: GOTO 100
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140 IF CV < > 32 THEN ST$(K) = C$ + ST$(K)
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150 J = 3
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160 K = K + 1
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170 IF K > 8 THEN K = 0
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180 GOTO 100
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REM Print the initial stack configuration.
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300 FOR I = 0 TO 8
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310 GOSUB 700
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320 NEXT I
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REM Consume input bytes until we are past the blank line and at the
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REM instructions. Newlines on the IIgs are carriage returns, '\r'.
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330 CL = 0
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340 GET C$: GET Z$
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350 IF CL = 13 AND ASC (C$) = 13 GOTO 400
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360 CL = ASC (C$)
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370 GOTO 340
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REM Begin reading and parsing instructions.
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REM We just need the three numbers in each instruction, so we consume
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REM everything (all non-digits) between.
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400 GET C$: GET Z$
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410 CV = ASC (C$)
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420 IF CV < 48 OR CV > 57 GOTO 400
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REM We've hit a number. Begin parsing that number into V, which was
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REM previously set to zero.
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430 V = V * 10 + CV - 48
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440 GET C$: GET Z$
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445 CV = ASC (C$)
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450 IF CV > 47 AND CV < 58 GOTO 430
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REM Put the value into its spot in the action array AC.
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REM If we have not finished reading in an action, go back to 400.
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460 AC(L) = V
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465 V = 0
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470 L = L + 1
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480 IF L < 3 GOTO 400
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REM Make "to" and "from" indices zero-based.
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490 AC(1) = AC(1) - 1
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495 AC(2) = AC(2) - 1
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REM Z$ stores the chunk being moved, and is added to its destination.
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500 Z$ = RIGHT$ (ST$(AC(1)),AC(0))
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510 ST$(AC(2)) = ST$(AC(2)) + Z$
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REM If we are emptying the "from" stack, set it to empty manually (LEFT$
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REM would fail otherwise). If not emptying, clip out the removed crates.
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520 Z = LEN (ST$(AC(1)))
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530 IF AC(0) = Z THEN ST$(AC(1)) = "": GOTO 600
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540 ST$(AC(1)) = LEFT$ (ST$(AC(1)),Z - AC(0))
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REM Time to update the visualization. Only update the two changed columns.
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REM Then, go back to 400 for the next instruction.
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REM When reading there fails at the end of the input file, the program will
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REM jump to 900 to exit.
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600 I = AC(1): GOSUB 700
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610 I = AC(2): GOSUB 700
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630 L = 0
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640 GOTO 400
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REM Stack rendering routine, expects index I into stack data ST$.
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REM Initial X and Y coordinates are set. GOTO 780 for return if stack is empty.
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700 X = I * 4 + 1
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705 Y = 25
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706 LE = LEN (ST$(I))
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708 IF LE = 0 GOTO 780
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REM Clear text above the current stack, in case the old stack was higher.
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REM VTAB and HTAB position the cursor. The semicolon in the PRINT statement
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REM omits the ending newline.
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710 FOR Z = 1 TO 24 - LE
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712 VTAB Z
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714 HTAB X
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716 PRINT " ";
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718 NEXT Z
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REM Build the stack from bottom to top.
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REM 760 exits if the stack is too tall.
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720 FOR Z = 1 TO LE
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730 VTAB Y - 1
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735 HTAB X
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740 PRINT "["; MID$ (ST$(I),Z,1);"]";
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750 Y = Y - 1
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760 IF Y = 1 THEN RETURN
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770 NEXT Z
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780 RETURN
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REM We land here after end-of-file. Close the file and exit.
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900 PRINT CHR$ (4),"CLOSE"
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910 END
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