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REM Advent of Code 2022: Day 6, part 1 and 2
REM Written in Applesoft BASIC
5 HOME
10 R1 = 3
20 R2 = 13
30 G1 = 0
40 G2 = 0
50 M = 0
50 PRINT CHR$ (4),"OPEN INPUT"
60 PRINT CHR$ (4),"READ INPUT"
70 ONERR GOTO 900
REM Print some fun messages, going for a hacker feel.
REM The routine at 1000 spins an empty FOR I = 0 TO A loop for a delay.
100 PRINT "INITIALIZING COMMUNICATION SYSTEM";
105 A = 350
110 FOR I = 0 TO 6
120 GOSUB 1000
130 PRINT ".";
140 NEXT I
150 PRINT
200 PRINT "OPENING SIGNAL DATASTREAM";
210 FOR I = 0 TO 6
220 GOSUB 1000
230 PRINT ".";
240 NEXT I
250 PRINT : PRINT
300 PRINT "SCANNING FOR START-OF-PACKET MARKER:"
310 HTAB 1
320 VTAB 8
330 PRINT "||||";
340 HTAB 1
350 VTAB 10
360 PRINT "||||||||||||||";
REM Main loop: Print the current string. If it can be checked for uniqueness,
REM GOTO 500 (which comes back to 440). At 440, we add the next character to
REM the string and trim off the end if its too long.
400 HTAB 1
403 VTAB 9
406 PRINT S$;
410 GET C$
413 S$ = C$ + S$
420 IF LEN (S$) > 40 THEN S$ = MID$ (S$,1,40)
430 IF M > 0 THEN M = M - 1: GOTO 400
440 IF G1 = 0 AND LEN (S$) > = 4 THEN GOSUB 500
450 IF G2 = 0 AND LEN (S$) > = 14 THEN GOSUB 2200
460 IF G1 = 1 AND G2 = 1 GOTO 900
480 GOTO 400
REM Here, we check for matching characters. It's hard-coded because there are
REM only a few combinations. A little ASCII art "connects" the matched bytes.
REM GOTO 700 if all unique, otherwise back to 440 for the next character.
500 R1 = R1 + 1
500 HTAB 1
510 VTAB 7
530 IF MID$ (S$,1,1) = MID$ (S$,2,1) THEN PRINT "/\ ";
540 IF MID$ (S$,1,1) = MID$ (S$,3,1) THEN PRINT "/-\ ";
550 IF MID$ (S$,1,1) = MID$ (S$,4,1) THEN PRINT "/--\";
560 IF MID$ (S$,2,1) = MID$ (S$,3,1) THEN PRINT " /\ ";
570 IF MID$ (S$,2,1) = MID$ (S$,4,1) THEN PRINT " /-\";
580 IF MID$ (S$,3,1) = MID$ (S$,4,1) THEN PRINT " /\";
590 PRINT " ";
700 HTAB 1
710 VTAB 13
715 A = 1300
718 G1 = 1
720 PRINT "MARKER FOUND AT INDEX ";R;"."
599 RETURN
REM I keep the exit routine at 900 out of habit.
900 PRINT CHR$ (4),"CLOSE"
910 END
REM The delay routine.
1000 FOR Z = 0 TO A: NEXT Z
1010 RETURN
REM Search for a matching pair. If found, store 2nd index in M.
2200 I = 1
2205 M = 0
2210 FOR J = I + 1 TO 14
2220 IF MID$ (S$,I,1) = MID$ (S$,J,1) THEN M = J:J = 14
2230 NEXT J
2240 IF M < > 0 GOTO 2300
REM If no matches, move to next index and repeat.
REM If we've gone through all indices, marker found. GOTO 2400.
2250 I = I + 1
2260 IF I < 14 GOTO 2200
2270 HTAB 1
2275 VTAB 23
2280 G2 = 1
2285 PRINT "MESSAGE FOUND AT INDEX ";R"."
2290 RETURN
REM A match was found. Show dashes between the two characters.
2300 HTAB I
2310 VTAB 11
2314 PRINT " ";
2318 HTAB I
2320 FOR J = I TO M
2330 PRINT "-";
2340 NEXT J
2345 M = 14 - M
2350 RETURN
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