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| author | Adam T. Carpenter <atc@53hor.net> | 2020-12-04 16:08:27 -0500 |
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| committer | Adam T. Carpenter <atc@53hor.net> | 2020-12-04 16:08:27 -0500 |
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| tree | c472e8a699424f263a74ad899be2cbe7db9c39a6 /posts/programming/2020-12-04-aoc-2020-day-1-in-cbm-basic.html | |
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diff --git a/posts/programming/2020-12-04-aoc-2020-day-1-in-cbm-basic.html b/posts/programming/2020-12-04-aoc-2020-day-1-in-cbm-basic.html new file mode 100644 index 0000000..34296d6 --- /dev/null +++ b/posts/programming/2020-12-04-aoc-2020-day-1-in-cbm-basic.html @@ -0,0 +1,237 @@ +<!DOCTYPE html> +<html> + <head> + <link rel="stylesheet" href="/includes/stylesheet.css" /> + <meta charset="utf-8" /> + <meta name="viewport" content="width=device-width, initial-scale=1" /> + <meta + property="og:description" + content="The World Wide Web pages of Adam Carpenter" + /> + <meta property="og:image" content="/includes/images/logo_diag.png" /> + <meta property="og:site_name" content="53hor.net" /> + <meta property="og:title" content="AOC 2020 Day 1 in CBM Basic" /> + <meta property="og:type" content="website" /> + <meta property="og:url" content="https://www.53hor.net" /> + <title>53hornet ➙ AOC 2020 Day 1 in CBM Basic</title> + </head> + + <body> + <nav> + <ul> + <li> + <a href="/"> + <img src="/includes/icons/home-roof.svg" /> + Home + </a> + </li> + <li> + <a href="/about.html"> + <img src="/includes/icons/information-variant.svg" /> + About + </a> + </li> + <li> + <a href="/software.html"> + <img src="/includes/icons/git.svg" /> + Software + </a> + </li> + <li> + <a href="/hosted.html"> + <img src="/includes/icons/desktop-tower.svg" /> + Hosted + </a> + </li> + <li> + <a type="application/rss+xml" href="/rss.xml"> + <img src="/includes/icons/rss.svg" /> + RSS + </a> + </li> + <li> + <a href="/contact.html"> + <img src="/includes/icons/at.svg" /> + Contact + </a> + </li> + </ul> + </nav> + + <article> + <h1>AOC 2020 Day 1 in CBM Basic</h1> + + <p class="description"> + I implemented the + <a href="https://adventofcode.com/2020">Advent of Code 2020</a> Day 1 + challenge in CBM BASIC on a real Commodore 64. I haven't done anything + in Basic in a long time, and probably never did anything actually + meaningful with it. Part 1 of the challenge was to take a list of + numbers, find the two that summed to 2020, and then multiply those two + numbers together. Part two was to perform part 1 but with three numbers + instead of two. + </p> + <p> + Now I wanted to actually write the code on the Commodore 64 itself, but + I gave myself some leniency. Instead of manually typing in all 200 + entries of input data (and inevitably making a breaking mistake) I used + Vim on my PC to format the <code>DATA</code> entries at the start of the + code. I then dropped that onto a 1541 disk image, plopped it on an SD + card, and used my SD2IEC to mount the SD card's image on the Commodore. + The rest of the programming was done on the Commodore itself. + </p> + + <p>Here is my solution for Day 1 Part 1:</p> + <pre> + <code> +10 DATA 1686, 1983, 1801, 1890, 1910, 1722, 1571, 1952, 1602, 1551, 1144 +11 DATA 1208, 1335, 1914, 1656, 1515, 1600, 1520, 1683, 1679, 1800, 1889 +12 DATA 1717, 1592, 1617, 1756, 1646, 1596, 1874, 1595, 1660, 1748, 1946 +13 DATA 1734, 1852, 2006, 1685, 1668, 1607, 1677, 403 , 1312, 1828, 1627 +14 DATA 1925, 1657, 1536, 1522, 1557, 1636, 1586, 1654, 1541, 1363, 1844 +15 DATA 1951, 1765, 1872, 696, 1764, 1718, 1540, 1493, 1947, 1786, 1548 +16 DATA 1981, 1861, 1589, 1707, 1915, 1755, 1906, 1911, 1628, 1980, 1986 +17 DATA 1780, 1645, 741 , 1727, 524 , 1690, 1732, 1956, 1523, 1534, 1498 +18 DATA 1510, 372 , 1777, 1585, 1614, 1712, 1650, 702 , 1773, 1713, 1797 +19 DATA 1691, 1758, 1973, 1560, 1615, 1933, 1281, 1899, 1845, 1752, 1542 +20 DATA 1694, 1950, 1879, 1684, 1809, 1988, 1978, 1843, 1730, 1377, 1507 +21 DATA 1506, 1566, 935 , 1851, 1995, 1796, 1900, 896 , 171, 1728, 1635 +22 DATA 1810, 2003, 1580, 1789, 1709, 2007, 1639, 1726, 1537, 1976, 1538 +23 DATA 1544, 1626, 1876, 1840, 1953, 1710, 1661, 1563, 1836, 1358, 1550 +24 DATA 1112, 1832, 1555, 1394, 1912, 1884, 1524, 1689, 1775, 1724, 1366 +25 DATA 1966, 1549, 1931, 1975, 1500, 1667, 1674, 1771, 1631, 1662, 1902 +26 DATA 1970, 1864, 2004, 2010, 504 , 1714, 1917, 1907, 1704, 1501, 1812 +27 DATA 1349, 1577, 1638, 1886, 1157, 1761, 1676, 1731, 2001, 1261, 1154 +28 DATA 1769, 1529 +100 DIM A(200) +110 FOR I=0TO199 +120 READ A(I) +140 NEXT +150 FOR I=0TO199 +160 B=A(I) +170 FOR J=0TO199 +180 IF I=J THEN 210 +190 C=A(J) +200 IF B+C=2020 THEN PRINT "!",B,C,B*C:STOP +210 NEXT J +220 NEXT I + </code></pre> + + <p> + I basically put all 200 numbers into data fields, and then defined an + array large enough to read them into with <code>DIM</code>. Then I + iterated over the array twice, checking each element against each other + element to see if they summed to 2020. If they did, I printed them both + and the product of the two found numbers and stopped further execution. + </p> + <p> + There weren't really any special tricks to this implementation except + remembering that I shouldn't be checking whether a number could sum to + 2020 with itself. + </p> + + <p> + Then I got to move onto Part 2, and this is where things got + interesting. Comparing any three numbers from the data meant the + cognitively easiest way to solve the problem was a triple loop. This of + course meant <code>O(n^3)</code> time, which the Commodore struggled + with. I waited about an hour before I decided I could optimize just a + little bit to speed up the search. + </p> + + <p> + I figured that for three numbers to sum to 2020, they all had to be + pretty small. Most likely they were most (if not all) three digits + instead of four. So I figured I could sort the entry data to make the + search finish probably near the start of the first layer of iteration. + Keep in mind I didn't want to pre-sort the data, I wanted the Commodore + to work with the same exact input set it had for Part 1. So I turned to + the simplest sorting algorithm I could remember: + <a href="https://en.wikipedia.org/wiki/Bubble_sort">bubble sort</a>. + </p> + + <p>Here is my solution for Day 1 Part 2:</p> + + <pre> + <code> +10 DATA 1686, 1983, 1801, 1890, 1910, 1722, 1571, 1952, 1602, 1551, 1144 +11 DATA 1208, 1335, 1914, 1656, 1515, 1600, 1520, 1683, 1679, 1800, 1889 +12 DATA 1717, 1592, 1617, 1756, 1646, 1596, 1874, 1595, 1660, 1748, 1946 +13 DATA 1734, 1852, 2006, 1685, 1668, 1607, 1677, 403 , 1312, 1828, 1627 +14 DATA 1925, 1657, 1536, 1522, 1557, 1636, 1586, 1654, 1541, 1363, 1844 +15 DATA 1951, 1765, 1872, 696, 1764, 1718, 1540, 1493, 1947, 1786, 1548 +16 DATA 1981, 1861, 1589, 1707, 1915, 1755, 1906, 1911, 1628, 1980, 1986 +17 DATA 1780, 1645, 741 , 1727, 524 , 1690, 1732, 1956, 1523, 1534, 1498 +18 DATA 1510, 372 , 1777, 1585, 1614, 1712, 1650, 702 , 1773, 1713, 1797 +19 DATA 1691, 1758, 1973, 1560, 1615, 1933, 1281, 1899, 1845, 1752, 1542 +20 DATA 1694, 1950, 1879, 1684, 1809, 1988, 1978, 1843, 1730, 1377, 1507 +21 DATA 1506, 1566, 935 , 1851, 1995, 1796, 1900, 896 , 171, 1728, 1635 +22 DATA 1810, 2003, 1580, 1789, 1709, 2007, 1639, 1726, 1537, 1976, 1538 +23 DATA 1544, 1626, 1876, 1840, 1953, 1710, 1661, 1563, 1836, 1358, 1550 +24 DATA 1112, 1832, 1555, 1394, 1912, 1884, 1524, 1689, 1775, 1724, 1366 +25 DATA 1966, 1549, 1931, 1975, 1500, 1667, 1674, 1771, 1631, 1662, 1902 +26 DATA 1970, 1864, 2004, 2010, 504 , 1714, 1917, 1907, 1704, 1501, 1812 +27 DATA 1349, 1577, 1638, 1886, 1157, 1761, 1676, 1731, 2001, 1261, 1154 +28 DATA 1769, 1529 +100 DIM A(200) +110 FOR I=0TO199 +120 READ A(I) +140 NEXT +141 GOSUB 300 +150 FOR I=0TO199 +160 B=A(I) +170 FOR J=0TO199 +180 IF J=I THEN 250 +190 C=A(J) +200 FOR K=0TO199 +210 IF K=I OR K=J THEN 240 +220 D=A(K) +230 IF B+C+D=2020 THEN PRINT "!",B,C,D,B*C*D:STOP +240 NEXT K +250 NEXT J +260 NEXT I +300 REM BUBBLE SORT +301 X=200 +310 N=200 +320 FOR I=0TON-2 +330 FOR J=0TON-I-2 +340 X=A(J):Y=A(J+1) +350 IF X>Y THEN A(J)=Y:A(J+1)=X +360 NEXT : NEXT +370 RETURN + </code> + </pre> + + <p> + I added a subroutine starting on line 300 to perform a basic bubble sort + on top of the original array of data. Now bubble sort isn't fast by any + means, but the Commodore was able to finish it in a couple of minutes. + And the results were worth it because the subsequent triple + <code>FOR</code>-loop completed in another few minutes. My instinct was + right and two of the solution numbers were triple-digit. + </p> + + <p> + So there you have it, Advent of Code 2020 Day 1 in Commodore 64 Basic + V2. You can run these samples on real hardware of course, or in an + emulator. You can also run them with the + <a href="https://github.com/mist64/cbmbasic"><code>cbmbasic</code></a> + interpreter, which is a neat native C64 Basic interpreter for modern + architectures. (Oh and I tested my samples on <code>cbmbasic</code> and + they finished instantaneously. It helps to have a + thousands-of-times-faster processor.) + </p> + + <p> + I was going to keep going with the challenge and finish them all in CBM + basic for fun, but the Day 2 input data set was 1000 entries. No + problem, I can just read them from a <code>SEQ</code> file. The only + blocker I realized was the challenge requires string character counting, + which I don't think there's a function for in CBM basic. Maybe I have to + do a few <code>PEEK</code>s and <code>POKE</code>s to check memory + locations for ASCII/PETSCII character codes. Or I could just put it off + til next year :) + </p> + </article> + </body> +</html> |