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166 lines
4.1 KiB
QBasic

REM Advent of Code 2022: Day 7, part 1 and 2
REM Written in Applesoft BASIC
REM Usual initialization. SPEED= sets the text speed; I play with it
REM and some empty FOR loops during the program for artistic effect.
10 ONERR GOTO 700
20 PRINT CHR$ (4),"OPEN INPUT"
30 PRINT CHR$ (4),"READ INPUT"
40 HOME
50 SPEED= 170
REM DN$ and DS are a index-matched "map" of paths and sizes. A size of
REM 200 accommodated my input.
REM W$ stores the current working directory.
100 DIM DN$(200)
110 DIM DS(200)
120 FOR I = 0 TO 199:DN$(I) = "": NEXT I
130 FOR I = 0 TO 199:DS(I) = 0: NEXT I
140 W$ = "/"
REM Main loop: consume a line of input, display it, and then handle
REM either the "ls" or "cd" that it is.
200 GOSUB 4000
210 PRINT "$";
215 FOR I = 0 TO 1000: NEXT I
218 SPEED= 70: PRINT RIGHT$ (S$, LEN (S$) - 1): SPEED= 170
220 IF LEFT$ (S$,4) = "$ cd" GOTO 300
230 GOTO 500
REM "cd" routine. If the path starts with '/', then clear the working
REM directory so we return to root.
REM If starting with a '.', GOTO 350 to handle backing up a level.
REM Otherwise, append to the working directory.
300 C$ = MID$ (S$,6,1)
305 IF ASC (C$) = 47 THEN W$ = ""
310 IF ASC (C$) = 46 GOTO 350
320 W$ = W$ + MID$ (S$,6, LEN (S$) - 5)
330 IF ASC ( RIGHT$ (W$,1)) < > 47 THEN W$ = W$ + "/"
340 GOTO 400
350 W$ = LEFT$ (W$, LEN (W$) - 1)
360 IF RIGHT$ (W$,1) < > "/" GOTO 350
370 GOTO 200
REM Call 2000 to create a size entry for this directory if it does not
REM exist.
400 S$ = W$
410 GOSUB 2000
420 GOTO 200
REM "ls" routine. Leave the loop if we reach the next command; skip dirs.
500 V = 0
510 GOSUB 4000
515 IF LEFT$ (S$,1) = "$" GOTO 210
520 PRINT S$
530 IF LEFT$ (S$,3) = "dir" GOTO 510
REM Call 3000 to add file's size to relevant directorys' totals.
540 V = VAL (S$)
550 S$ = W$
560 GOSUB 3000
570 GOTO 510
REM We will land here once the file has been completely read. Do the
REM search for part 1, summing into T.
700 T = 0
710 FOR I = 0 TO 199
720 IF LEN (DN$(I)) = 0 THEN I = 199: GOTO 740
730 IF DS(I) < = 100000 THEN T = T + DS(I)
740 NEXT I
745 PRINT
750 PRINT "part 1: ";T;" bytes"
REM Part 2 is at 5000. It will come back to 900 to exit.
760 GOTO 5000
900 PRINT CHR$ (4),"CLOSE"
910 SPEED= 255
920 END
REM Subroutine: Fetches the size of directory S$, putting it in V.
1000 V = 0
1010 FOR I = 0 TO 199
1020 IF DN$(I) = S$ THEN V = DS(I):I = 199
1030 NEXT I
1040 RETURN
REM Subroutine: Initializes new entry for directory S$.
2000 FOR I = 0 TO 199
2010 IF DN$(I) = S$ THEN PRINT "ERROR": END
2020 IF LEN (DN$(I)) = 0 THEN DN$(I) = S$:DS(I) = 0:I = 199
2030 NEXT I
2040 RETURN
REM Subroutine: Adds size V to entry for directory S$ and its parents.
3000 FOR I = 0 TO 199
3010 L = LEN (S$)
3015 M = LEN (DN$(I))
3020 IF LEN (DN$(I)) = 0 THEN I = 199: GOTO 3040
3030 IF L > = M AND LEFT$ (S$,M) = DN$(I) GOTO 3060
3040 NEXT I
3050 RETURN
3060 DS(I) = DS(I) + V
3080 GOTO 3040
REM Subroutine: Reads next line of input from the file.
4000 S$ = ""
4010 GET C$
4020 IF ASC (C$) < 32 GOTO 4050
4030 S$ = S$ + C$
4040 GOTO 4010
4050 RETURN
REM Part 2. Start by printing total filesystem size.
5000 PRINT "$ ";
5002 SPEED= 70: PRINT "df -h": SPEED= 170
5004 FOR I = 0 TO 1000: NEXT I
5006 S$ = "/"
5010 GOSUB 1000
5015 PRINT V
REM Calculate free memory requirements.
5020 UN = 70000000 - V
5030 RE = 30000000 - UN
5040 DE = 99999999
5100 PRINT "$";
5110 SPEED= 70: PRINT " cleanup": SPEED= 170
5120 FOR I = 0 TO 1000: NEXT I
5130 PRINT "NEED TO FREE ";RE;" BYTES..."
REM The actual work: iterate for smallest entry that is at least RE bytes.
5200 FOR I = 0 TO 199
5210 IF LEN (DN$(I)) = 0 THEN I = 199: GOTO 5230
5220 IF DS(I) > RE AND DS(I) < DE THEN DE = DS(I)
5230 NEXT I
REM All done!
5240 PRINT "FREED ";DE;" BYTES."
5250 GOTO 900
REM Debug subroutine: print all contents of directory/size map.
6000 FOR I = 0 TO 199
6010 IF LEN (DN$(I)) = 0 THEN I = 199: GOTO 6030
6020 PRINT DN$(I),DS(I)
6030 NEXT I
6040 RETURN