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)
- Code block support is not fully rolled out yet but likely will be in the middle of the event. Try to share solutions as both code blocks and using something such as https://topaz.github.io/paste/ or pastebin (code blocks to future proof it for when 0.19 comes out and since code blocks currently function in some apps and some instances as well if they are running a 0.19 beta)
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
1 point
*
[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);
}
1 point
*
4 points
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
2 points
2 points
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
3 points
(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=}")
2 points
*
Factor on github (with comments and imports):
: line>cards ( line -- winning-nums player-nums )
":|" split rest
[
[ CHAR: space = ] trim
split-words harvest [ string>number ] map
] map first2
;
: points ( winning-nums player-nums -- n )
intersect length
dup 0 > [ 1 - 2^ ] when
;
: part1 ( -- )
"vocab:aoc-2023/day04/input.txt" utf8 file-lines
[ line>cards points ] map-sum .
;
: follow-card ( i commons -- n )
[ 1 ] 2dip
2dup nth swapd
over + (a..b]
[ over follow-card ] map-sum
nip +
;
: part2 ( -- )
"vocab:aoc-2023/day04/input.txt" utf8 file-lines
[ line>cards intersect length ] map
dup length swap '[ _ follow-card ]
map-sum .
;