Day 4: Scratchcards
Megathread guidelines
- Keep top level comments as only solutions, if you want to say something other than a solution put it in a new post. (replies to comments can be whatever)
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FAQ
- What is this?: Here is a post with a large amount of details: https://programming.dev/post/6637268
- Where do I participate?: https://adventofcode.com/
- Is there a leaderboard for the community?: We have a programming.dev leaderboard with the info on how to join in this post: https://programming.dev/post/6631465
🔒This post will be unlocked when there is a decent amount of submissions on the leaderboard to avoid cheating for top spots
🔓 Unlocked after 8 mins
[JavaScript] Swapped over to javascript from rust since I want to also practice some js. Managed to get part 1 in 4 minutes and got top 400 on the global leaderboard. Second part took a bit longer and took me 13 mins since I messed up by originally trying to append to the card array. (eventually swapped to keeping track of amounts in a separate array)
Part 1
// Part 1
// ======
function part1(input) {
const lines = input.split("\n");
let sum = 0;
for (const line of lines) {
const content = line.split(":")[1];
const winningNums = content.split("|")[0].match(/\d+/g);
const myNums = content.split("|")[1].match(/\d+/g);
let cardSum = 0;
for (const num of winningNums) {
if (myNums.includes(num)) {
if (cardSum == 0) {
cardSum = 1;
} else {
cardSum = cardSum * 2;
}
}
}
sum = sum + cardSum;
}
return sum;
}
Part 2
// Part 2
// ======
function part2(input) {
let lines = input.split("\n");
let amount = Array(lines.length).fill(1);
for (const [i, line] of lines.entries()) {
const content = line.split(":")[1];
const winningNums = content.split("|")[0].match(/\d+/g);
const myNums = content.split("|")[1].match(/\d+/g);
let cardSum = 0;
for (const num of winningNums) {
if (myNums.includes(num)) {
cardSum += 1;
}
}
for (let j = 1; j <= cardSum; j++) {
if (i + j >= lines.length) {
break;
}
amount[i + j] += amount[i];
}
}
return lines.reduce((acc, line, i) => {
return acc + amount[i];
}, 0);
}
Haskell
11:39 – I spent most of the time reading the scoring rules and (as usual) writing a parser…
import Control.Monad
import Data.Bifunctor
import Data.List
readCard :: String -> ([Int], [Int])
readCard =
join bimap (map read) . second tail . break (== "|") . words . tail . dropWhile (/= ':')
countShared = length . uncurry intersect
part1 = sum . map ((\n -> if n > 0 then 2 ^ (n - 1) else 0) . countShared)
part2 = sum . foldr ((\n a -> 1 + sum (take n a) : a) . countShared) []
main = do
input <- map readCard . lines <$> readFile "input04"
print $ part1 input
print $ part2 input
Ruby
Somehow took way longer on the second part than the first part trying a recursive approach and then realizing that was dumb.
https://github.com/snowe2010/advent-of-code/blob/master/ruby_aoc/2023/day04/day04.rb
Edit: Sorry, should have read your code first, you made it work too. if it works it works, Recursive solutions just click for me over other solutions.
I made the recursion work, went to a depth of 24 for my input set.
Recursive C#
internal class Day4Task2 : IRunnable
{
private Regex _regex = new Regex("Card\\s*\\d*: ([\\d\\s]{2} )*\\|( [\\d\\s]{2})*");
private Dictionary _matchCountCache = new Dictionary();
private int _maxDepth = 0;
public void Run()
{
var inputLines = File.ReadAllLines("Days/Four/Day4Input.txt");
int sumScore = 0;
for (int i = 0; i < inputLines.Length; i++)
{
sumScore += ScoreCard(i, inputLines, 0);
Console.WriteLine("!!!" + i + "!!!");
}
Console.WriteLine("Sum:"+sumScore.ToString());
Console.WriteLine("Max Recursion Depth:"+ _maxDepth.ToString());
}
private int ScoreCard(int lineId, string[] inputLines, int depth)
{
if( depth > _maxDepth )
{
_maxDepth = depth;
}
if(lineId >= inputLines.Length)
{
return 0;
}
int matchCount = 0;
if (!_matchCountCache.ContainsKey(lineId)) {
var winningSet = new HashSet();
var matches = _regex.Match(inputLines[lineId]);
foreach (Capture capture in matches.Groups[1].Captures)
{
winningSet.Add(capture.Value.Trim());
}
foreach (Capture capture in matches.Groups[2].Captures)
{
if (winningSet.Contains(capture.Value.Trim()))
{
matchCount++;
}
}
_matchCountCache[lineId] = matchCount;
}
matchCount = _matchCountCache[lineId];
int totalCards = 1;
while(matchCount > 0)
{
totalCards += ScoreCard(lineId+matchCount, inputLines, depth+1);
matchCount--;
}
//Console.WriteLine("Finished processing id: " + lineId + " Sum is: " + totalCards);
return totalCards;
}
}
(python) Much easier than day 3.
code
import pathlib
base_dir = pathlib.Path(__file__).parent
filename = base_dir / "day4_input.txt"
with open(base_dir / filename) as f:
lines = f.read().splitlines()
score = 0
extra_cards = [0 for _ in lines]
n_cards = [1 for _ in lines]
for i, line in enumerate(lines):
_, numbers = line.split(":")
winning, have = numbers.split(" | ")
winning_numbers = {int(n) for n in winning.split()}
have_numbers = {int(n) for n in have.split()}
have_winning_numbers = winning_numbers & have_numbers
n_matches = len(have_winning_numbers)
if n_matches:
score += 2 ** (n_matches - 1)
j = i + 1
for _ in range(n_matches):
if j >= len(lines):
break
n_cards[j] += n_cards[i]
j += 1
answer_p1 = score
print(f"{answer_p1=}")
answer_p2 = sum(n_cards)
print(f"{answer_p2=}")
Nim
This one was pretty simple, just parse the numbers into sets and check the size of the intersection. Part 2 just made the scoring mechanism a little more complicated.
Hi there! Looks like you linked to a Lemmy community using a URL instead of its name, which doesn’t work well for people on different instances. Try fixing it like this: !nim@programming.dev
That’s some elegant code! Then again, I suppose that’s the beauty of nim.
I’m rather spoiled by python, so I feel like it could be more elegant. xD
But yeah, I do like how this one turned out, and nim runs a whole lot faster than python does. I really like nim’s “method call syntax”. Instead of having methods associated with an individual type, you can just call any procedure as x.f(remaining_args) to call f with x as its first argument. Makes it easy to chain procedures. Since nim is strongly typed, it’ll know which procedure you mean to use by the signature.
Aside from the general conciseness, the “universal function call syntax” is my favorite aspect of nim.
If you want to take chaining procedures to the next level, try a concatenative language like Factor (I have a day 4 solution in this thread – with no assignment to variables).
I also suggest having a look at Roc if you want a functional programming adventure, which offers great chaining syntax, a very friendly community, and is in an exciting development phase.