10progsize%=400
20DIM prog% progsize%
30datasize%=323*4
40DIM data% datasize%
50FOR O%=0 TO 3 STEP 3
60P%=prog%
70PROCprog
80IF P%-prog% > progsize% THEN ERROR 255, "Prog too big " + STR$(P%-prog%)
90NEXT
100CALL loaddata
105!&81 = 1
106?&85 = 0
110 PROCrun_path(3,1)
120PRINT "Part 1: "; !&81
130PROCrun_path(1,1)
140PROCrun_path(5,1)
150PROCrun_path(7,1)
160PROCrun_path(1,2)
170PRINT "Part 2: ";
175CALL printforty
178PRINT
180END
190DEF PROCrun_path(xstep%,ystep%)
200X%=xstep%
210Y%=ystep%
220CALL counttrees
230 LOCAL trees%
240trees%=!&74 AND &FFFF
250PRINT STR$(xstep%);",";STR$(ystep%);" trees=";STR$(trees%)
260CALL mult
265ENDPROC
270DEF PROCprog
280[OPT O%
290.loaddata
300LDA #&40 \ open file for input
310LDX #filename AND &FF
320LDY #filename DIV 256
330JSR &FFCE \ OSFIND
340ORA #0
350BNE gotfile
360BRK
370EQUB &FF
380EQUS "Error opening file"
390EQUB 13
400.gotfile
410TAY
420LDA #data% AND &FF
430STA &70
440LDA #data% DIV 256
450STA &71
460LDX #0
470.startbyte
480LDA #0
490STA (&70, X)
500LDA #1 \ bit
510STA &72
520.byteloop
530JSR &FFD7 \ OSBGET
540CMP #&FE
550BCS enddata
560JSR &FFEE \ OSWRCH
570CMP #10
580BNE notendline
590LDA #13
600JSR &FFEE \ OSWRCH
610JMP endbyte
620.notendline
630CMP #ASC("#")
640BNE nottree
650LDA (&70, X)
660ORA &72
670STA (&70, X)
680.nottree
690ASL &72
700BNE byteloop
710.endbyte
720CLC
730LDA &70
740ADC #1
750STA &70
760LDA &71
770ADC #0
780STA &71
790JMP startbyte
800.enddata
810LDA #0 \ close file
820JMP &FFCE \ OSFIND
830.counttrees
840\ set &70 to %data
850LDA #data% AND &FF
860STA &70
870LDA #data% DIV 256
880STA &71
890\ &72 will be the x-offset
900STX &72
910\ &76 will be the y-offset to add in bytes
920TYA
930ASL A:ASL A
940STA &76
950\ &73 is the bit to test
960LDA #1
970STA &73
980\ Y is the byte offset in the row
990LDY #0
1000\ &74,5 is the count of trees
1010STY &74
1020STY &75
1030.loop
1040\ move to the next line in the data
1050LDA &70
1060CLC
1070ADC &76
1080STA &70
1090LDA &71
1100ADC #0
1110STA &71
1120\ check if we've reached the end
1130CMP #(data% + datasize%) DIV 256
1140BCC notdataend
1150LDA &70
1160CMP #(data% + datasize%) AND &FF
1170BCS printresults
1180.notdataend
1190\ add horizontal offset
1200LDA &72
1210LSR A:LSR A:LSR A
1220STY &80
1230CLC
1240ADC &80
1250TAY
1260LDA &72
1270AND #7
1280TAX
1290.shiftloop
1300ASL &73
1310BNE notnextbyte
1320LDA #1
1330STA &73
1340INY
1350.notnextbyte
1360DEX
1370BNE shiftloop
1380\ check if we've gone off the end of the line
1390CPY #3
1400BCC notlineend
1410 BNE lineend
1420LDA &73
1430BPL notlineend \ line end when bit 7 set
1440.lineend
1450\ subtract 31 from the x-pos
1460DEY:DEY:DEY
1470LDX #7
1480 .subloop
1490LSR (&73)
1500BNE notsubbyte
1510DEY
1520LDA #&80
1530STA &73
1540.notsubbyte
1550DEX
1560BNE subloop
1570.notlineend
1580\ test whether there's a tree
1590LDA (&70), Y
1600AND &73
1610BEQ loop
1620\ add to the tree count
1630CLC
1640LDA &74
1650ADC #1
1660STA &74
1670LDA &75
1680ADC #0
1690STA &75
1700JMP loop
1710.printresults
1720RTS
1730.filename
1740EQUS "data"
1750EQUB 13
1770\ routine to multiply a 5-byte integer in &81 by an 8-bit number in &74 and store the result in &81
1780.mult
1790 \ number to add in &86, clear result in &81
1800 LDX #4
1810.copyloop
1820LDA &81, X
1830STA &86, X
1831 LDA #0
1832STA &81, X
1840DEX
1850BPL copyloop
1860 .multloop
1890LSR &74
1900\ add value if bit was set
1910BCC nomultadd
1920CLC
1930 LDX #&80 - 5
1940.multaddloop
1950 LDA &86 + 5 - &80, X
1960 ADC &81 + 5 - &80, X
1970 STA &81 + 5 - &80, X
1980 INX
1990BPL multaddloop
2000.nomultadd
2010\ multiply the number to add by 2
2020ASL &86
2030ROL &87
2040ROL &88
2050ROL &89
2060ROL &8A
2070\ check if the multiplier is zero
2080LDA &74
2090BNE multloop
2100RTS
2110\ routine to divide 5-byte number in &81 by 10
2115 .divforty
2120LDX #40 \ 40 bits
2130LDA #0
2140.divloop
2150ASL &81
2160ROL &82
2170ROL &83
2180ROL &84
2190ROL &85
2200ROL A
2210CMP #10
2220BCC divnobit
2230SBC #10
2240INC &81
2250.divnobit
2260DEX
2270BNE divloop
2280RTS
2290\ routine to print 5-byte number in &81. Uses &70-&7e as scratch space
2300\ corrupts number in &81
2310.printforty
2320\ generate 13 digits
2330 LDY #12
2335 .pfortyloop
2340 JSR divforty
2350\ remainder in a
2360CLC
2370ADC #ASC("0")
2380STA &70, Y
2390DEY
2400BPL pfortyloop
2410INY
2420.skiploop \ skip leading zeros
2430LDA &70, Y
2440CMP #ASC("0")
2450BNE doneskip
2460INY
2470CPY #12 \ leave at least one digit
2480BCC skiploop
2485.doneskip
2490.pdigitloop
2500LDA &70, Y
2510JSR &FFEE
2520INY
2530CPY #13
2540BCC pdigitloop
2550RTS
2560]
2570ENDPROC