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🍷 - 2024 DAY 3 SOLUTIONS -🍷

Day 3: Mull It Over

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FAQ

54 comments

  • I started poking at doing a proper lexer/parser, but then I thought about how early in AoC it is and how low the chance is that the second part will require proper parsing.

    So therefore; hello regex my old friend, I've come to talk with you again.

  • Uiua

    Uses experimental feature of fold to track the running state of do/don't.

    [edit] Slightly re-written to make it less painful :-) Try it online! 

     undefined
        
# Experimental!
DataP₁       ← $ xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))
DataP₂       ← $ xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))
GetMul       ← $ mul\((\d{1,3}),(\d{1,3})\)
GetMulDoDont ← $ mul\(\d{1,3},\d{1,3}\)|do\(\)|don\'t\(\)

&p/+≡(/×≡⋕↘1)regexGetMul DataP₁ # Part 1

# Build an accumulator to track running state of do/don't
Filter ← ↘1⊂:∧(⍣(0 °"don"|1 °"do("|.◌)) :1≡(↙3°□)
≡⊢ regex GetMulDoDont DataP₂
▽⊸≡◇(≍"mul"↙3)▽⊸Filter      # Apply Filter, remove the spare 'do's
&p/+≡◇(/×≡◇⋕↘1⊢regexGetMul) # Get the digits and multiply, sum.

  • Factor

     undefined
        
: 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 ;

  • J

    We can take advantage of the manageable size of the input to avoid explicit looping and mutable state; instead, construct vectors which give, for each character position in the input, the position of the most recent do() and most recent don't(); for part 2 a multiplication is enabled if the position of the most recent do() (counting start of input as 0) is greater than that of the most recent don't() (counting start of input as minus infinity). 

     undefined
        
load 'regex'

raw =: fread '3.data'
mul_matches =: 'mul\(([[:digit:]]{1,3}),([[:digit:]]{1,3})\)' rxmatches raw

NB. a b sublist y gives elements [a..b) of y
sublist =: ({~(+i.)/)~"1 _

NB. ". is number parsing
mul_results =: */"1 ". (}."2 mul_matches) sublist raw
result1 =: +/ mul_results

do_matches =: 'do\(\)' rxmatches raw
dont_matches =: 'don''t\(\)' rxmatches raw
match_indices =: (<0 0) & {"2
do_indices =: 0 , match_indices do_matches  NB. start in do mode
dont_indices =: match_indices dont_matches
NB. take successive diffs, then append length from last index to end of string
run_lengths =: (}. - }:) , (((#raw) & -) @: {:)
do_map =: (run_lengths do_indices) # do_indices
dont_map =: (({. , run_lengths) dont_indices) # __ , dont_indices
enabled =: do_map > dont_map
result2 =: +/ ((match_indices mul_matches) { enabled) * mul_results

  • Rust with nom parser

    Decided to give it a go with the nom parser (first time using this crate). Turned out quite nicely. Had some issues with the alt combinator: All alternatives have to return the same type, using a enum to wrap all options did the trick. 

     undefined
        
use memmap2::Mmap;
use nom::{
    branch::alt, bytes::complete::*, character::complete::*, combinator::map, multi::many_till,
    sequence::tuple, AsBytes, IResult,
};

#[derive(Debug)]
enum Token {
    Do,
    Dont,
    Mul(u64, u64),
}

fn main() -> anyhow::Result<()> {
    let file = std::fs::File::open("input.txt")?;
    let mmap = unsafe { Mmap::map(&file)? };

    let mut sum_part1 = 0;
    let mut sum_part2 = 0;
    let mut enabled = true;

    let mut cursor = mmap.as_bytes();
    while let Ok(token) = parse(cursor) {
        match token.1 .1 {
            Token::Do => enabled = true,
            Token::Dont => enabled = false,
            Token::Mul(left, right) => {
                let prod = left * right;
                sum_part1 += prod;
                if enabled {
                    sum_part2 += prod;
                }
            }
        }

        cursor = token.0;
    }

    println!("part1: {} part2: {}", sum_part1, sum_part2);

    Ok(())
}

type ParseResult<'a> =
    Result<(&'a [u8], (Vec<char>, Token)), nom::Err<nom::error::Error<&'a [u8]>>>;

fn parse(input: &[u8]) -> ParseResult {
    many_till(
        anychar,
        alt((
            map(doit, |_| Token::Do),
            map(dont, |_| Token::Dont),
            map(mul, |el| Token::Mul(el.2, el.4)),
        )),
    )(input)
}

fn doit(input: &[u8]) -> IResult<&[u8], &[u8]> {
    tag("do()")(input)
}

fn dont(input: &[u8]) -> IResult<&[u8], &[u8]> {
    tag("don't()")(input)
}

type ParsedMulResult<'a> = (&'a [u8], &'a [u8], u64, &'a [u8], u64, &'a [u8]);

fn mul(input: &[u8]) -> IResult<&[u8], ParsedMulResult> {
    tuple((tag("mul"), tag("("), u64, tag(","), u64, tag(")")))(input)
}

  • 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. 

     gleam
        
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 })
}

  • Python

    After a bunch of fiddling yesterday and today I finally managed to arrive at a regex-only solution for part 2. That re.DOTALL is crucial here. 

     python
        
import re
from pathlib import Path


def parse_input_one(input: str) -> list[tuple[int]]:
    p = re.compile(r"mul\((\d{1,3}),(\d{1,3})\)")
    return [(int(m[0]), int(m[1])) for m in p.findall(input)]


def parse_input_two(input: str) -> list[tuple[int]]:
    p = re.compile(r"don't\(\).*?do\(\)|mul\((\d{1,3}),(\d{1,3})\)", re.DOTALL)
    return [(int(m[0]), int(m[1])) for m in p.findall(input) if m[0] and m[1]]


def part_one(input: str) -> int:
    pairs = parse_input_one(input)
    return sum(map(lambda v: v[0] * v[1], pairs))


def part_two(input: str) -> int:
    pairs = parse_input_two(input)
    return sum(map(lambda v: v[0] * v[1], pairs))


if __name__ == "__main__":
    input = Path("input").read_text("utf-8")
    print(part_one(input))
    print(part_two(input))

  • Nim

     nim
        
import ../aoc, re, sequtils, strutils, math

proc mulsum*(line:string):int=
  let matches = line.findAll(re"mul\([0-9]{1,3},[0-9]{1,3}\)")
  let pairs = matches.mapIt(it[4..^2].split(',').map(parseInt))
  pairs.mapIt(it[0]*it[1]).sum

proc filter*(line:string):int=
  var state = true;
  var i=0
  while i < line.len:
    if state:
      let off = line.find("don't()", i)
      if off == -1:
        break
      result += line[i..<off].mulsum
      i = off+6
      state = false
    else:
      let on = line.find("do()", i)
      if on == -1:
        break
      i = on+4
      state = true
      
  if state:
    result += line[i..^1].mulsum

proc solve*(input:string): array[2,int] =
  #part 1&2
  result = [input.mulsum, input.filter]

    I had a nicer solution in mind for part 2, but for some reason nre didn't want to work for me, and re couldn't give me the start/end or all results, so I ended up doing this skip/toggle approach.

    Also initially I was doing it line by line out of habit from other puzzles, but then ofc the don't()s didn't propagate to the next line.

  • Rust

     rust
        
use crate::utils::read_lines;

pub fn solution1() {
    let lines = read_lines("src/day3/input.txt");
    let sum = lines
        .map(|line| {
            let mut sum = 0;
            let mut command_bytes = Vec::new();
            for byte in line.bytes() {
                match (byte, command_bytes.as_slice()) {
                    (b')', [.., b'0'..=b'9']) => {
                        handle_mul(&mut command_bytes, &mut sum);
                    }
                    _ if matches_mul(byte, &command_bytes) => {
                        command_bytes.push(byte);
                    }
                    _ => {
                        command_bytes.clear();
                    }
                }
            }

            sum
        })
        .sum::<usize>();

    println!("Sum of multiplication results = {sum}");
}

pub fn solution2() {
    let lines = read_lines("src/day3/input.txt");

    let mut can_mul = true;
    let sum = lines
        .map(|line| {
            let mut sum = 0;
            let mut command_bytes = Vec::new();
            for byte in line.bytes() {
                match (byte, command_bytes.as_slice()) {
                    (b')', [.., b'0'..=b'9']) if can_mul => {
                        handle_mul(&mut command_bytes, &mut sum);
                    }
                    (b')', [b'd', b'o', b'(']) => {
                        can_mul = true;
                        command_bytes.clear();
                    }
                    (b')', [.., b't', b'(']) => {
                        can_mul = false;
                        command_bytes.clear();
                    }
                    _ if matches_do_or_dont(byte, &command_bytes)
                        || matches_mul(byte, &command_bytes) =>
                    {
                        command_bytes.push(byte);
                    }
                    _ => {
                        command_bytes.clear();
                    }
                }
            }

            sum
        })
        .sum::<usize>();

    println!("Sum of enabled multiplication results = {sum}");
}

fn matches_mul(byte: u8, command_bytes: &[u8]) -> bool {
    matches!(
        (byte, command_bytes),
        (b'm', [])
            | (b'u', [.., b'm'])
            | (b'l', [.., b'u'])
            | (b'(', [.., b'l'])
            | (b'0'..=b'9', [.., b'(' | b'0'..=b'9' | b','])
            | (b',', [.., b'0'..=b'9'])
    )
}

fn matches_do_or_dont(byte: u8, command_bytes: &[u8]) -> bool {
    matches!(
        (byte, command_bytes),
        (b'd', [])
            | (b'o', [.., b'd'])
            | (b'n', [.., b'o'])
            | (b'\'', [.., b'n'])
            | (b'(', [.., b'o' | b't'])
            | (b't', [.., b'\''])
    )
}

fn handle_mul(command_bytes: &mut Vec<u8>, sum: &mut usize) {
    let first_num_index = command_bytes
        .iter()
        .position(u8::is_ascii_digit)
        .expect("Guarunteed to be there");
    let comma_index = command_bytes
        .iter()
        .position(|&c| c == b',')
        .expect("Guarunteed to be there.");

    let num1 = bytes_to_num(&command_bytes[first_num_index..comma_index]);
    let num2 = bytes_to_num(&command_bytes[comma_index + 1..]);

    *sum += num1 * num2;
    command_bytes.clear();
}

fn bytes_to_num(bytes: &[u8]) -> usize {
    bytes
        .iter()
        .rev()
        .enumerate()
        .map(|(i, digit)| (*digit - b'0') as usize * 10usize.pow(i as u32))
        .sum::<usize>()
}

    Definitely not my prettiest code ever. It would probably look nicer if I used regex or some parsing library, but I took on the self-imposed challenge of not using third party libraries. Also, this is already further than I made it last year!

  • Raku

     undefined
        
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

  • 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. 

     undefined
        
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

  • Rust feat. pest

    No Zalgo here! I wasted a huge amount of time by not noticing that the second part's example input was different - my code worked fine but my test failed 🤦‍♂️

    pest.rs is lovely, although part two made my PEG a bit ugly. 

     pest
        
part1    =  { SOI ~ (mul_expr | junk)+ ~ EOI }
part2    =  { (enabled | disabled)+ ~ EOI }
mul_expr =  { "mul(" ~ number ~ "," ~ number ~ ")" }
number   =  { ASCII_DIGIT{1,3} }
junk     = _{ ASCII }
on       = _{ "do()" }
off      = _{ "don't()" }
enabled  = _{ (SOI | on) ~ (!(off) ~ (mul_expr | junk))+ }
disabled = _{ off ~ (!(on) ~ junk)+ }

  
     rust
        
use std::fs;

use color_eyre::eyre;
use pest::Parser;
use pest_derive::Parser;

#[derive(Parser)]
#[grammar = "memory.pest"]
pub struct MemoryParser;

fn parse(input: &str, rule: Rule) -> eyre::Result<usize> {
    let sum = MemoryParser::parse(rule, input)?
        .next()
        .expect("input must be ASCII")
        .into_inner()
        .filter(|pair| pair.as_rule() == Rule::mul_expr)
        .map(|pair| {
            pair.into_inner()
                .map(|num| num.as_str().parse::<usize>().unwrap())
                .product::<usize>()
        })
        .sum();
    Ok(sum)
}

fn part1(filepath: &str) -> eyre::Result<usize> {
    let input = fs::read_to_string(filepath)?;
    parse(&input, Rule::part1)
}

fn part2(filepath: &str) -> eyre::Result<usize> {
    let input = fs::read_to_string(filepath)?;
    parse(&input, Rule::part2)
}

fn main() -> eyre::Result<()> {
    color_eyre::install()?;

    let part1 = part1("d03/input.txt")?;
    let part2 = part2("d03/input.txt")?;
    println!("Part 1: {part1}\nPart 2: {part2}");
    Ok(())
}

  • I did part 2 live with the python interactive shell. I deleted all the stuff where I was just exploring ideas.

    part 1: 

     undefined
        
import re

def multiply_and_add(data: "str") -> int:
    digit_matches = re.findall(r"mul\(\d{0,3},\d{0,3}\)", data)
    result = 0
    for _ in digit_matches:
        first = _.split("(")[1].split(")")[0].split(",")[0]
        second = _.split("(")[1].split(")")[0].split(",")[1]
        result += int(first) * int(second)

    return result

with open("input") as file:
    data = file.read()


answer = multiply_and_add(data)
print(answer)

    part 2: 

     undefined
        
Python 3.11.2 (main, Aug 26 2024, 07:20:54) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import solution2
<re.Match object; span=(647, 651), match='do()'>
>>> from solution2 import *
>>> split_on_dont = data.split("don't()")
>>> valid = []
>>> valid.append(split_on_dont[0])
>>> for substring in split_on_dont[1:]:
...     subsubstrings = substring.split("do()", maxsplit=1)
...     for subsubstring in subsubstrings[1:]:
...             valid.append(subsubstring)
...
>>> answer = 0
>>> for _ in valid:
...     answer += multiply_and_add(_)
...
>>> answer
103811193

  • Smalltalk

    I wrote matchesActual cause all of smalltalk'sstupid matchesDo: or whatever don't give you the actual match with captures, only substrings (that wasted a good 40 minutes).

    Also smalltalk really needs an index operator 

     smalltalk
        
day3p1: input
  | reg sum |
    reg := 'mul\((\d\d?\d?),(\d\d?\d?)\)' asRegex.
    sum := 0.
    
    reg matchesActual: input do: [ :m | " + sum at end cause operator precedence"
        sum := (m subexpression: 2) asInteger * (m subexpression: 3) asInteger + sum 
    ].
    
    ^ sum.


  
     smalltalk
        
day3p2: input
  | reg sum do val |

    reg := 'do(\:?n''t)?\(\)|mul\((\d{1,3}),(\d{1,3})\)' asRegex.
    sum := 0.
    do := true.
    reg matchesActual: input do: [ :m |
        val := m subexpression: 1.
        (val at: 1) = $d ifTrue: [ do := (val size < 5) ]
        ifFalse: [ 
            do ifTrue: [ 
                sum := (m subexpression: 2) asInteger * (m subexpression: 3) asInteger + sum.
        ].  ].
    ].
    
    ^ sum.
54 comments