Python

I’m surprised I don’t see more people taking advantage of eval I thought it was pretty slick.

import operator 
import re

with open('input.txt', 'r') as file:
    memory = file.read()

matches = re.findall("mul\(\d{1,3},\d{1,3}\)|don't\(\)|do\(\)", memory)

enabled = 1
filtered_matches = []
for instruction in matches:
    if instruction == "don't()":
        enabled = 0
        continue
    elif instruction == "do()":
        enabled = 1
        continue
    elif enabled: 
        filtered_matches.append(instruction)
multipled = [eval(f"operator.{x}") for x in filtered_matches]
print(sum(multiples))

Kotlin

Just the standard Regex stuff. I found this website to be very helpful to write the patterns. (Very useful in general)

fun main() {
    fun part1(input: List<String>): Int =
        Regex("""mul\(\d+,\d+\)""").findAll(input.joinToString()).sumOf {
            with(Regex("""\d+""").findAll(it.value)) { this.first().value.toInt() * this.last().value.toInt() }
        }

    fun part2(input: List<String>): Int {
        var isMultiplyInstructionEnabled = true  // by default
        return Regex("""mul\(\d+,\d+\)|do\(\)|don't\(\)""").findAll(input.joinToString()).fold(0) { acc, instruction ->
            when (instruction.value) {
                "do()" -> acc.also { isMultiplyInstructionEnabled = true }
                "don't()" -> acc.also { isMultiplyInstructionEnabled = false }
                else -> {
                    if (isMultiplyInstructionEnabled) {
                        acc + with(Regex("""\d+""").findAll(instruction.value)) { this.first().value.toInt() * this.last().value.toInt() }
                    } else acc
                }
            }
        }
    }

    val testInputPart1 = readInput("Day03_test_part1")
    val testInputPart2 = readInput("Day03_test_part2")
    check(part1(testInputPart1) == 161)
    check(part2(testInputPart2) == 48)

    val input = readInput("Day03")
    part1(input).println()
    part2(input).println()
}

´´´

Python

Part1:

matches = re.findall(r"(mul\((\d+),(\d+)\))", input)
muls = [int(m[1]) * int(m[2]) for m in matches]
print(sum(muls))

Part2:

instructions = list(re.findall(r"(do\(\)|don't\(\)|(mul\((\d+),(\d+)\)))", input)
mul_enabled = True
muls = 0

for inst in instructions:
    if inst[0] == "don't()":
        mul_enabled = False
    elif inst[0] == "do()":
        mul_enabled = True
    elif mul_enabled:
        muls += int(inst[2]) * int(inst[3])

print(muls)

Gleam

Struggled with the second part as I am still very new to this very cool language, but got there after scrolling for some inspiration.

import gleam/int
import gleam/io
import gleam/list
import gleam/regex
import gleam/result
import gleam/string
import simplifile

pub fn main() {
  let assert Ok(data) = simplifile.read("input.in")
  part_one(data) |> io.debug
  part_two(data) |> io.debug
}

fn part_one(data) {
  let assert Ok(multiplication_pattern) =
    regex.from_string("mul\\(\\d{1,3},\\d{1,3}\\)")
  let assert Ok(digit_pattern) = regex.from_string("\\d{1,3},\\d{1,3}")
  let multiplications =
    regex.scan(multiplication_pattern, data)
    |> list.flat_map(fn(reg) {
      regex.scan(digit_pattern, reg.content)
      |> list.map(fn(digits) {
        digits.content
        |> string.split(",")
        |> list.map(fn(x) { x |> int.parse |> result.unwrap(0) })
        |> list.reduce(fn(a, b) { a * b })
        |> result.unwrap(0)
      })
    })
    |> list.reduce(fn(a, b) { a + b })
    |> result.unwrap(0)
}

fn part_two(data) {
  let data = "do()" <> string.replace(data, "\n", "") <> "don't()"
  let assert Ok(pattern) = regex.from_string("do\\(\\).*?don't\\(\\)")
  regex.scan(pattern, data)
  |> list.map(fn(input) { input.content |> part_one })
  |> list.reduce(fn(a, b) { a + b })
}

Rust

Didn’t do anything crazy here – ended up using regex like a bunch of other folks.

use regex::Regex;

use crate::shared::util::read_lines;

fn parse_mul(input: &[String]) -> (u32, u32) {
    // Lazy, but rejoin after having removed `\n`ewlines.
    let joined = input.concat();
    let re = Regex::new(r"mul\((\d+,\d+)\)|(do\(\))|(don't\(\))").expect("invalid regex");

    // part1
    let mut total1 = 0u32;
    // part2 -- adds `do()`s and `don't()`s
    let mut total2 = 0u32;
    let mut enabled = 1u32;

    re.captures_iter(&joined).for_each(|c| {
        let (_, [m]) = c.extract();
        match m {
            "do()" => enabled = 1,
            "don't()" => enabled = 0,
            _ => {
                let product: u32 = m.split(",").map(|s| s.parse::<u32>().unwrap()).product();
                total1 += product;
                total2 += product * enabled;
            }
        }
    });
    (total1, total2)
}

pub fn solve() {
    let input = read_lines("inputs/day03.txt");
    let (part1_res, part2_res) = parse_mul(&input);
    println!("Part 1: {}", part1_res);
    println!("Part 2: {}", part2_res);
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_solution() {
        let test_input = vec![
            "xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))".to_string(),
        ];
        let (p1, p2) = parse_mul(&test_input);
        eprintln!("P1: {p1}, P2: {p2}");
        assert_eq!(161, p1);
        assert_eq!(48, p2);
    }
}

Solution on my github (Made it public now)

Python

def process(input, part2=False):
    if part2:
        input = re.sub(r'don\'t\(\).+?do\(\)', '', input) # remove everything between don't() and do()
    total = [ int(i[0]) * int(i[1]) for i in re.findall(r'mul\((\d+),(\d+)\)', input) ]
    return sum(total)

Given the structure of the input file, we just have to ignore everything between don’t() and do(), so remove those from the instructions before processing.

Julia

I did not try to make my solution concise and kept separate code for part 1 and part 2 with test cases for both to check if I broke anything. But after struggling with Day 2 I am quite pleased to have solved Day 3 with only a little bugfixing.

function calcLineResult(line::String)
	lineResult::Int = 0
	enabled::Bool = true
	for i=1 : length(line)
		line[i]!='m' ? continue : (i<length(line) ? i+=1 : continue)
		line[i]!='u' ? continue : (i<length(line) ? i+=1 : continue)
		line[i]!='l' ? continue : (i<length(line) ? i+=1 : continue)
		line[i]!='(' ? continue : (i<length(line) ? i+=1 : continue)
		num1Str::String = ""
		while line[i] in ['0','1','2','3','4','5','6','7','8','9'] #should check for length of digits < 3, but works without
			num1Str = num1Str*line[i]; (i<length(line) ? i+=1 : continue)
		end
		line[i]!=',' ? continue : (i<length(line) ? i+=1 : continue)
		num2Str::String = ""
		while line[i] in ['0','1','2','3','4','5','6','7','8','9'] #should check for length of digits < 3, but works without
			num2Str = num2Str*line[i]; (i<length(line) ? i+=1 : continue)
		end
		line[i]==')' ? lineResult+=parse(Int,num1Str)*parse(Int,num2Str) : continue
	end
	return lineResult
end

function calcLineResultWithEnabling(line::String,enabled::Bool)
	lineResult::Int = 0
	for i=1 : length(line)
		if enabled && line[i] == 'm'
			i<length(line) ? i += 1 : continue
			line[i]!='u' ? continue : (i<length(line) ? i+=1 : continue)
			line[i]!='l' ? continue : (i<length(line) ? i+=1 : continue)
			line[i]!='(' ? continue : (i<length(line) ? i+=1 : continue)
			num1Str::String = ""
			while line[i] in ['0','1','2','3','4','5','6','7','8','9']
				num1Str = num1Str*line[i]; (i<length(line) ? i+=1 : continue)
			end
			line[i]!=',' ? continue : (i<length(line) ? i+=1 : continue)
			num2Str::String = ""
			while line[i] in ['0','1','2','3','4','5','6','7','8','9']
				num2Str = num2Str*line[i]; (i<length(line) ? i+=1 : continue)
			end
			line[i]==')' ? lineResult+=parse(Int,num1Str)*parse(Int,num2Str) : continue
		elseif line[i] == 'd'
			i<length(line) ? i += 1 : continue
			line[i]!='o' ? continue : (i<length(line) ? i+=1 : continue)
			if line[i] == '('
				i<length(line) ? i += 1 : continue
				line[i]==')' ? enabled=true : continue
				#@info i,line[i-3:i]
			elseif line[i] == 'n'
				i<length(line) ? i += 1 : continue
				line[i]!=''' ? continue : (i<length(line) ? i+=1 : continue)
				line[i]!='t' ? continue : (i<length(line) ? i+=1 : continue)
				line[i]!='(' ? continue : (i<length(line) ? i+=1 : continue)
				line[i]==')' ? enabled=false : continue
				#@info i,line[i-6:i]
			else
				nothing
			end
		end
	end
	return lineResult,enabled
end

function calcMemoryResult(inputFile::String,useEnabling::Bool)
	memoryRes::Int = 0
	f = open(inputFile,"r")
	lines = readlines(f)
	close(f)
	enabled::Bool = true
	for line in lines
		if useEnabling
			lineRes::Int,enabled = calcLineResultWithEnabling(line,enabled)
			memoryRes += lineRes
		else
			memoryRes += calcLineResult(line)
		end
	end
	return memoryRes
end

if abspath(PROGRAM_FILE) == @__FILE__
	@info "Part 1"
	@debug "checking test input"
	inputFile::String = "day03InputTest"
	memoryRes::Int = calcMemoryResult(inputFile,false)
	try
		@assert memoryRes==161
	catch e
		throw(ErrorException("$e memoryRes=$memoryRes"))
	end
	@debug "test input ok"
	@debug "running real input"
	inputFile::String = "day03Input"
	memoryRes::Int = calcMemoryResult(inputFile,false)
	try
		@assert memoryRes==153469856
	catch e
		throw(ErrorException("$e memoryRes=$memoryRes"))
	end
	println("memory result: $memoryRes")
	@debug "real input ok"

	@info "Part 2"
	@debug "checking test input"
	inputFile::String = "day03InputTest"
	memoryRes::Int = calcMemoryResult(inputFile,true)
	try
		@assert memoryRes==48
	catch e
		throw(ErrorException("$e memoryRes=$memoryRes"))
	end
	@debug "test input ok"
	@debug "running real input"
	inputFile::String = "day03Input"
	memoryRes::Int = calcMemoryResult(inputFile,true)
	try
		@assert memoryRes==77055967
	catch e
		throw(ErrorException("$e memoryRes=$memoryRes"))
	end
	println("memory result: $memoryRes")
	@debug "real input ok"

end

Uiua

Part 1:

&fras "day3/input.txt"
/+≡/×≡⋕≡↘1regex "mul\\((\\d+),(\\d+)\\)"

Part 2:

Filter ← ⍜⊜∘≡⋅""⊸⦷°□
.&fras "day3/input.txt"
∧Filter♭regex"don't\\(\\)?(.*?)(?:do\\(\\)|$)"
/+≡/×≡⋕≡↘1regex "mul\\((\\d+),(\\d+)\\)"

python

import re
import aoc

def setup():
    return (aoc.get_lines(3), 0)

def one():
    lines, acc = setup()
    for line in lines:
        ins = re.findall(r'mul\(\d+,\d+\)', line)
        for i in ins:
            p = [int(x) for x in re.findall(r'\d+', i)]
            acc += p[0] * p[1]
    print(acc)

def two():
    lines, acc = setup()
    on = 1
    for line in lines:
        ins = re.findall(r"do\(\)|don't\(\)|mul\(\d+,\d+\)", line)
        for i in ins:
            if i == "do()":
                on = 1
            elif i == "don't()":
                on = 0
            elif on:
                p = [int(x) for x in re.findall(r'\d+', i)]
                acc += p[0] * p[1]
    print(acc)

one()
two()

Factor

: get-input ( -- corrupted-input )
  "vocab:aoc-2024/03/input.txt" utf8 file-contents ;

: get-muls ( corrupted-input -- instructions )
  R/ mul\(\d+,\d+\)/ all-matching-subseqs ;

: process-mul ( instruction -- n )
  R/ \d+/ all-matching-subseqs
  [ string>number ] map-product ;

: solve ( corrupted-input -- n )
  get-muls [ process-mul ] map-sum ;

: part1 ( -- n )
  get-input solve ;

: part2 ( -- n )
  get-input
  R/ don't\(\)(.|\n)*?do\(\)/ split concat
  R/ don't\(\)(.|\n)*/ "" re-replace
  solve ;

I couldn’t figure it out in haskell, so I went with bash for the first part

Shell

cat example | grep -Eo "mul\([[:digit:]]{1,3},[[:digit:]]{1,3}\)" | cut -d "(" -f 2 | tr -d ")" | tr "," "*" | paste -sd+ | bc

but this wouldn’t rock anymore in the second part, so I had to resort to python for it

Python

import sys

f = "\n".join(sys.stdin.readlines())

f = f.replace("don't()", "\ndon't()\n")
f = f.replace("do()", "\ndo()\n")

import re

enabled = True
muls = []
for line in f.split("\n"):
    if line == "don't()":
        enabled = False
    if line == "do()":
        enabled = True
    if enabled:
        for match in re.finditer(r"mul\((\d{1,3}),(\d{1,3})\)", line):
            muls.append(int(match.group(1)) * int(match.group(2)))
        pass
    pass

print(sum(muls))

Go

Part 1, just find the regex groups, parse to int, and done.

func part1() {
	file, _ := os.Open("input.txt")
	defer file.Close()
	scanner := bufio.NewScanner(file)

	re := regexp.MustCompile(`mul\(([0-9]{1,3}),([0-9]{1,3})\)`)
	product := 0

	for scanner.Scan() {
		line := scanner.Text()
		submatches := re.FindAllStringSubmatch(line, -1)

		for _, s := range submatches {
			a, _ := strconv.Atoi(s[1])
			b, _ := strconv.Atoi(s[2])
			product += (a * b)
		}
	}

	fmt.Println(product)
}

Part 2, not so simple. Ended up doing some weird hack with a map to check if the multiplication was enabled or not. Also instead of finding regex groups I had to find the indices, and then interpret what those mean… Not very readable code I’m afraid

func part2() {
	file, _ := os.Open("input.txt")
	defer file.Close()
	scanner := bufio.NewScanner(file)

	mulRE := regexp.MustCompile(`mul\(([0-9]{1,3}),([0-9]{1,3})\)`)
	doRE := regexp.MustCompile(`do\(\)`)
	dontRE := regexp.MustCompile(`don't\(\)`)
	product := 0
	enabled := true

	for scanner.Scan() {
		line := scanner.Text()
		doIndices := doRE.FindAllStringIndex(line, -1)
		dontIndices := dontRE.FindAllStringIndex(line, -1)
		mulSubIndices := mulRE.FindAllStringSubmatchIndex(line, -1)

		mapIndices := make(map[int]string)
		for _, do := range doIndices {
			mapIndices[do[0]] = "do"
		}
		for _, dont := range dontIndices {
			mapIndices[dont[0]] = "dont"
		}
		for _, mul := range mulSubIndices {
			mapIndices[mul[0]] = "mul"
		}

		nextMatch := 0

		for i := 0; i < len(line); i++ {
			val, ok := mapIndices[i]
			if ok && val == "do" {
				enabled = true
			} else if ok && val == "dont" {
				enabled = false
			} else if ok && val == "mul" {
				if enabled {
					match := mulSubIndices[nextMatch]
					a, _ := strconv.Atoi(string(line[match[2]:match[3]]))
					b, _ := strconv.Atoi(string(line[match[4]:match[5]]))
					product += (a * b)
				}
				nextMatch++
			}
		}
	}

	fmt.Println(product)
}

Sorry for the delay posting this one, Ategon seemed to have it covered, so I forgot :D I will do better.

Raku

sub MAIN($input) {
    grammar Muls {
        token TOP { .*? <mul>+%.*? .* }
        token mul { "mul(" <number> "," <number> ")" }
        token number { \d+ }
    }

    my $parsedMuls = Muls.parsefile($input);
    my @muls = $parsedMuls<mul>.map({.<number>».Int});
    my $part-one-solution = @muls.map({[*] $_.List}).sum;
    say "part 1: $part-one-solution";

    grammar EnabledMuls {
        token TOP { .*? [<.disabled> || <mul>]+%.*? .* }
        token mul { "mul(" <number> "," <number> ")" }
        token number { \d+ }
        token disabled { "don't()" .*? ["do()" || $] }
    }

    my $parsedEnabledMuls = EnabledMuls.parsefile($input);
    my @enabledMuls = $parsedEnabledMuls<mul>.map({.<number>».Int});
    my $part-two-solution = @enabledMuls.map({[*] $_.List}).sum;
    say "part 2: $part-two-solution";
}

github

Haskell

module Main where

import Control.Arrow hiding ((+++))
import Data.Char
import Data.Functor
import Data.Maybe
import Text.ParserCombinators.ReadP hiding (get)
import Text.ParserCombinators.ReadP qualified as P

data Op = Mul Int Int | Do | Dont deriving (Show)

parser1 :: ReadP [(Int, Int)]
parser1 = catMaybes <$> many ((Just <$> mul) <++ (P.get $> Nothing))

parser2 :: ReadP [Op]
parser2 = catMaybes <$> many ((Just <$> operation) <++ (P.get $> Nothing))

mul :: ReadP (Int, Int)
mul = (,) <$> (string "mul(" *> (read <$> munch1 isDigit <* char ',')) <*> (read <$> munch1 isDigit <* char ')')

operation :: ReadP Op
operation = (string "do()" $> Do) +++ (string "don't()" $> Dont) +++ (uncurry Mul <$> mul)

foldOp :: (Bool, Int) -> Op -> (Bool, Int)
foldOp (_, n) Do = (True, n)
foldOp (_, n) Dont = (False, n)
foldOp (True, n) (Mul a b) = (True, n + a * b)
foldOp (False, n) _ = (False, n)

part1 = sum . fmap (uncurry (*)) . fst . last . readP_to_S parser1
part2 = snd . foldl foldOp (True, 0) . fst . last . readP_to_S parser2

main = getContents >>= print . (part1 &&& part2)