Input parsing AGAIN?

-- SPDX-FileCopyrightText: 2023 Jummit
--
-- SPDX-License-Identifier: GPL-3.0-or-later

local lines = {}
for line in io.open("3.input"):lines() do
	table.insert(lines, "."..line..".")
end
local width = #lines[1]
local height = #lines
local function at(x, y, w)
	if y < 1 or y > height then return nil end
	return lines[y]:sub(x, x + w - 1)
end
local sum = 0
local gears = {}
for y, line in ipairs(lines) do
	local start = 1
	local outLine = line
	while true do
		local newStart, numEnd = line:find("%d+", start)
		if not newStart then break end
		local symbol = false
		local num = tonumber(line:sub(newStart, numEnd))
		for y = y - 1, y + 1 do
			local surrounding = at(newStart - 1, y, numEnd - newStart + 3)
			if surrounding then
				if surrounding and surrounding:match("[^.%d]") then
					symbol = true
				end
				for i = 1, #surrounding do
					local gear = surrounding:sub(i, i) == "*"
					if gear then
						if not gears[y] then
							gears[y] = {}
						end
						local x = i + newStart - 2
						if not gears[y][x] then
							gears[y][i + newStart - 2] = {}
						end
						table.insert(gears[y][x], num)
					end
				end
			end
		end
		if symbol then
			sum = sum + num
		end
		start = numEnd + 1
	end
end
print(sum)
local ratio = 0
for _, line in pairs(gears) do
	for _, gears in pairs(line) do
		if #gears == 2 then
			ratio = ratio + gears[1] * gears[2]
		end
	end
end
print(ratio)

// SPDX-FileCopyrightText: 2023 Jummit
//
// SPDX-License-Identifier: GPL-3.0-or-later

use strings;
use regex;
use fmt;
use os;
use bufio;
use io;
use strconv;
use types;

fn star_in(lines: []str, x: uint, y: uint, w: uint) bool = {
	let start = y;
	if (start > 0) start -= 1;
	let end = y + 1;
	if (end >= len(lines)) end -= 1;
	const re = regex::compile(`[^.0-9]`)!;
	for (let h = start; h <= end; h += 1) {
		fmt::println(strings::sub(lines[h], x, x + w))!;
		if (regex::test(&re, strings::sub(lines[h], x, x + w))) {
			fmt::println("")!;
			return true;
		};
	};
	fmt::println("")!;
	return false;
};

export fn main() void = {
	const file = os::open("3.input")!;
	defer io::close(file)!;
	const buf = bufio::newscanner(file, types::SIZE_MAX);
	let lines: []str = [];
	defer strings::freeall(lines);
	for (true) {
		match (bufio::scan_line(&buf)!) {
		case io::EOF =>
			break;
		case let line: const str =>
			append(lines, strings::dup(line));
		};
	};
	const height = len(lines);
	const width = len(lines[0]);
	let sum: uint = 0;
	let gears: [](uint, uint) = [];
	const num_re = regex::compile(`[0-9]+`)!;
	for (let y = 0u; y < len(lines); y += 1) {
		let nums = regex::findall(&num_re, lines[y]);
		defer regex::result_freeall(nums);
		for (let i = 0z; i < len(nums); i += 1) {
			for (let j = 0z; j < len(nums[i]); j += 1) {
				const find = nums[i][j];
				const num = strconv::stou(find.content)!;
				let start = find.start: uint;
				let w = len(find.content): uint + 2;
				if (start > 0) {
					start -= 1;
				} else {
					w -= 1;
				};
				if (star_in(lines, start, y, w)) {
					sum += num;
				};
			};
		};
	};
	fmt::printfln("{}", sum)!;
};

Only had the time to solve part 1, but had a lot of fun with it. Here’s my solution: d03/p1

Python solution

just more parsing problems

I get the feeling that I should include some default types for handling 2D maps in my boilerplate, it’s a very recurring problem in AoC after all.

My solution is reasonably simplistic - and therefore also a bit slow, but the design meant I could do part 2 with just a few extra lines of code on the already processed data, here’s the functional part of it; (I push the previous days solution as part of my workflow for starting with the current day so the full code won’t be up until tomorrow)

Point = Struct.new('Point', :x, :y)
PartNumber = Struct.new('PartNumber', :number, :adjacent) do
  def adjacent?(to); adjacent.include?(to); end
  def irrelevant?; adjacent.empty?; end
  def to_i; number; end
end

class Implementation
  def initialize
    @map = []; @dim = { width: 0, height: 0 }; @symbols = []; @numbers = []
  end

  def input(line)
    @dim[:width] = line.size; @dim[:height] += 1
    @map += line.chars
  end

  def calc
    for y in (0..@dim[:height]-1) do
      for x in (0..@dim[:width]-1) do
        chr = get(x, y); next if chr =~ /\d/ || chr == '.'
        @symbols << Point.new(x, y)
      end
    end

    for y in (0..@dim[:height]-1) do
      buf = ""; adj = []
      for x in (0..@dim[:width]) do # Going one over, to fake a non-number as an end char on all lines
        chr = get(x, y)
        if chr =~ /\d/
          buf += chr
          (-1..1).each do |adj_x|
            (-1..1).each do |adj_y|
              next if adj_x == 0 && adj_y == 0 ||
                (x + adj_x < 0) || (x + adj_x >= @dim[:width]) ||
                (y + adj_y < 0) || (y + adj_y >= @dim[:height])
              sym = Point.new(x + adj_x, y + adj_y)
              adj << sym if @symbols.any? sym
            end
          end
        elsif !buf.empty?
          @numbers << PartNumber.new(buf.to_i, adj)
          buf = ""; adj = []
        end
      end
    end
  end

  def output
    part1 = @numbers.reject(&:irrelevant?).map(&:to_i).sum
    puts "Part 1:", part1

    gears = @symbols.select do |sym|
      next unless get(sym) == '*'
      next unless @numbers.select { |num| num.adjacent? sym }.size == 2
      true
    end
    part2 = gears.sum { |gear| @numbers.select { |num| num.adjacent? gear }.map(&:to_i).inject(:*) }

    puts "Part 2:", part2
  end

  private

  def get(x, y = -1)
    y = x.y if x.is_a?(Point)
    x = x.x if x.is_a?(Point)
    return unless (0..@dim[:width]-1).include?(x) && (0..@dim[:height]-1).include?(y)

    @map[y * @dim[:width] + x % @dim[:width]]
  end
end

Edit: Updated now with part 2.

Managed to have a crack at this a bit earlier today, I’ve only done Part 01 so far. I’ll update with Part 02 later.

I tackled this with the personal challenge of not loading the entire puzzle input into memory, which would have made this a bit easier.

Solution in Rust 🦀

View formatted on GitLab

use std::{
    env, fs,
    io::{self, BufRead, BufReader, Read},
};

fn main() -> io::Result<()> {
    let args: Vec = env::args().collect();
    let filename = &args[1];
    let file1 = fs::File::open(filename)?;
    let file2 = fs::File::open(filename)?;
    let reader1 = BufReader::new(file1);
    let reader2 = BufReader::new(file2);

    println!("Part one: {}", process_part_one(reader1));
    println!("Part two: {}", process_part_two(reader2));
    Ok(())
}

fn process_part_one(reader: BufReader) -> u32 {
    let mut lines = reader.lines().peekable();
    let mut prev_line: Option = None;
    let mut sum = 0;
    while let Some(line) = lines.next() {
        let current_line = line.expect("line exists");
        let next_line = match lines.peek() {
            Some(Ok(line)) => Some(line),
            Some(Err(_)) => None,
            None => None,
        };
        match (prev_line, next_line) {
            (None, Some(next)) => {
                let lines = vec![¤t_line, next];
                sum += parse_lines(lines, true);
            }
            (Some(prev), Some(next)) => {
                let lines = vec![&prev, ¤t_line, next];
                sum += parse_lines(lines, false);
            }
            (Some(prev), None) => {
                let lines = vec![&prev, ¤t_line];
                sum += parse_lines(lines, false);
            }
            (None, None) => {}
        }

        prev_line = Some(current_line);
    }
    sum
}

fn process_part_two(reader: BufReader) -> u32 {
    let mut lines = reader.lines().peekable();
    let mut prev_line: Option = None;
    let mut sum = 0;
    while let Some(line) = lines.next() {
        let current_line = line.expect("line exists");
        let next_line = match lines.peek() {
            Some(Ok(line)) => Some(line),
            Some(Err(_)) => None,
            None => None,
        };
        match (prev_line, next_line) {
            (None, Some(next)) => {
                let lines = vec![¤t_line, next];
                sum += parse_lines_for_gears(lines, true);
            }
            (Some(prev), Some(next)) => {
                let lines = vec![&prev, ¤t_line, next];
                sum += parse_lines_for_gears(lines, false);
            }
            (Some(prev), None) => {
                let lines = vec![&prev, ¤t_line];
                sum += parse_lines_for_gears(lines, false);
            }
            (None, None) => {}
        }

        prev_line = Some(current_line);
    }

    sum
}

fn parse_lines(lines: Vec<&String>, first_line: bool) -> u32 {
    let mut sum = 0;
    let mut num = 0;
    let mut valid = false;
    let mut char_vec: Vec> = Vec::new();
    for line in lines {
        char_vec.push(line.chars().collect());
    }
    let chars = match first_line {
        true => &char_vec[0],
        false => &char_vec[1],
    };
    for i in 0..chars.len() {
        if chars[i].is_digit(10) {
            // Add the digit to the number
            num = num * 10 + chars[i].to_digit(10).expect("is digit");

            // Check the surrounding character for non-period symbols
            for &x in &[-1, 0, 1] {
                for chars in &char_vec {
                    if (i as isize + x).is_positive() && ((i as isize + x) as usize) < chars.len() {
                        let index = (i as isize + x) as usize;
                        if !chars[index].is_digit(10) && chars[index] != '.' {
                            valid = true;
                        }
                    }
                }
            }
        } else {
            if valid {
                sum += num;
            }
            valid = false;
            num = 0;
        }
    }
    if valid {
        sum += num;
    }
    sum
}

fn parse_lines_for_gears(lines: Vec<&String>, first_line: bool) -> u32 {
    let mut sum = 0;
    let mut char_vec: Vec> = Vec::new();
    for line in &lines {
        char_vec.push(line.chars().collect());
    }
    let chars = match first_line {
        true => &char_vec[0],
        false => &char_vec[1],
    };
    for i in 0..chars.len() {
        if chars[i] == '*' {
            let surrounding_nums = get_surrounding_numbers(&lines, i);
            let product = match surrounding_nums.len() {
                0 | 1 => 0,
                _ => surrounding_nums.iter().product(),
            };
            sum += product;
        }
    }
    sum
}

fn get_surrounding_numbers(lines: &Vec<&String>, gear_pos: usize) -> Vec {
    let mut nums: Vec = Vec::new();
    let mut num: u32 = 0;
    let mut valid = false;
    for line in lines {
        for (i, char) in line.chars().enumerate() {
            if char.is_digit(10) {
                num = num * 10 + char.to_digit(10).expect("is digit");
                if [gear_pos - 1, gear_pos, gear_pos + 1].contains(&i) {
                    valid = true;
                }
            } else if num > 0 && valid {
                nums.push(num);
                num = 0;
                valid = false;
            } else {
                num = 0;
                valid = false;
            }
        }
        if num > 0 && valid {
            nums.push(num);
        }
        num = 0;
        valid = false;
    }
    nums
}

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

    const INPUT: &str = "467..114..
...*......
..35..633.
......#...
617*......
.....+.58.
..592.....
......755.
...$.*....
.664.598..";

    #[test]
    fn test_process_part_one() {
        let input_bytes = INPUT.as_bytes();
        assert_eq!(4361, process_part_one(BufReader::new(input_bytes)));
    }

    #[test]
    fn test_process_part_two() {
        let input_bytes = INPUT.as_bytes();
        assert_eq!(467835, process_part_two(BufReader::new(input_bytes)));
    }
}

That was not fun to solve. Lots of ugly code. This is a less ugly second version. Language: Nim.

day_03.nim

I wrote today’s program in Python. (I am going to do a different language each day.) The only thing that gave me a little trouble was I was counting “\n” as a part label. Once I realized that I was able to get both problems done very quickly.

My code for the two parts is on github:-

• https://github.com/pngwen/advent-2023/blob/main/day-3a.py
• https://github.com/pngwen/advent-2023/blob/main/day-3b.py

Language: C#

I aimed at keeping it as simple and short as reasonably possible this time, no overbuilding here!

I even used a goto to let me break out of multiple loops at once 🤮 (I had to look up how they worked!) I would totally fail me in a code review!

internal class Day3 : IRunnable
    {
        public void Run()
        {
            var input = File.ReadAllLines("Days/Three/Day3Input.txt");
            int sum = 0;
            string numStr = "";
            var starMap = new Dictionary<(int,int),List>();
            for (int i = 0; i < input.Length; i++)           
                for (int j = 0; j < input[i].Length; j++)
                {
                    if (char.IsDigit(input[i][j]))                    
                        numStr += input[i][j];                    
                    if (numStr.Length > 0 && (j == input[i].Length - 1 || !char.IsDigit(input[i][j + 1])))
                    {
                        for (int k = Math.Max(0, i - 1); k < Math.Min(i + 2, input.Length); k++)                        
                            for (int l = Math.Max(0, j - numStr.Length); l < Math.Min(j + 2, input[i].Length); l++)                            
                                if (!char.IsDigit(input[k][l]) && input[k][l] != '.')
                                {
                                    sum += int.Parse(numStr);
                                    if (input[k][l] == '*')
                                    {
                                        if (starMap.ContainsKey((k, l)))                                        
                                            starMap[(k, l)].Add(int.Parse(numStr));                                        
                                        else
                                            starMap.Add((k,l),new List { int.Parse(numStr) });
                                    }
                                    goto endSymbSearch;
                                }                           
                    endSymbSearch:
                        numStr = "";
                    }
                }            
            Console.WriteLine("Result1:"+sum.ToString());
            Console.WriteLine("Result2:" + starMap.Where(sm => sm.Value.Count == 2).Sum(sm => sm.Value[0] * sm.Value[1]));
        }
    }

[LANGUAGE: C#]

I kept trying to create clever solutions, but ended up falling back on regex when it was taking to long. THE TLDR is we scan the list of strings for a symbol, then parse the three lines above, below and inline with the symbol for digits. Then we try and match the indexes of the match and the area around the symbol. Part 2 was a small modification, and was mostly about getting the existing code to conform the data into a pattern for each of the three lines.

Part 1

static char[] Symbols = { '@', '#', '$', '%', '&', '*', '/', '+', '-', '=' };
string pattern = @"\d+";
static List? list;
list = new List((await File.ReadAllLinesAsync(@".\Day 3\PuzzleInput.txt")));

int count = 0;
for (int row = 0; row < list.Count; row++)
{
    for (int col = 0; col < list[row].Length; col++)
    {
        var c = list[row][col];
        if (c == '.')
        {
            continue;
        }

        if (Symbols.Contains(c))
        {
            var res = Calculate(list[row - 1], col);
            res += Calculate(list[row], col);
            res += Calculate(list[row + 1], col);
            count += res;
        }

    }
}
Console.WriteLine(count);

private static int Calculate(string line, int col)
{
    List indexesToCheck = new List { col - 1, col, col + 1 };
    int count = 0;
    MatchCollection matches = Regex.Matches(line, pattern);

    foreach (Match match in matches)
    {
        string number = match.Value;

        if (AnyIndexInList(indexesToCheck, match.Index, match.Length))
        {
            count += Int32.Parse(number);
        }
    }
    return count;
}

static bool AnyIndexInList(List list, int startIndex, int length)
{
    for (int i = startIndex; i < startIndex + length; i++)
    {
        if (list.Contains(i))
        {
            return true;
        }
    }
    return false;
}

Part 2:

list = new List((await File.ReadAllLinesAsync(@".\Day 3\PuzzleInput.txt")));

int count = 0;
for (int row = 0; row < list.Count; row++)
{
    for (int col = 0; col < list[row].Length; col++)
    {
        var c = list[row][col];
        if (c == '.')
            continue;
        
        if (c == '*')
        {
            var res1 = Calculate2(list[row - 1], col);
            var res2 = Calculate2(list[row], col);
            var res3 = Calculate2(list[row + 1], col);

            count += (res1, res2, res3) switch 
            {
                {res1: not null, res2: null, res3: null } when  res1[1] != null => res1[0].Value * res1[1].Value,
                {res1:  null, res2: not null, res3: null } when res2[1] != null => res2[0].Value * res2[1].Value,
                {res1:  null, res2: null, res3: not null } when res3[1] != null => res3[0].Value * res3[1].Value,

                {res1: not null, res2: not null, res3: null } => res1[0].Value * res2[0].Value,
                {res1: not null, res2: null, res3: not null } => res1[0].Value * res3[0].Value,
                {res1: null, res2: not null, res3: not null } => res2[0].Value * res3[0].Value,
                {res1: not null, res2: not null, res3: not null } => res1[0].Value * res2[0].Value * res3[0].Value,

                _ => 0
            } ;
        }
    }
}
                
Console.WriteLine(count);


private static int?[]? Calculate2(string line, int col)
{
    List indexesToCheck = new List { col - 1, col, col + 1 };
    int?[]? count = null;
    MatchCollection matches = Regex.Matches(line, pattern);

    foreach (Match match in matches)
    {
        string number = match.Value;

        if (AnyIndexInList(indexesToCheck, match.Index, match.Length))
        {
            if (count == null)
                count = new int?[2] { Int32.Parse(number), null };
            else {
                count[1] = Int32.Parse(number);
            };
        }
    }
    return count;
}

Factor on github:

USING: arrays io.encodings.utf8 io.files kernel make math
math.intervals math.parser prettyprint sequences
sequences.extras splitting unicode ;
IN: aoc-2023.day03

: symbol-indices ( line -- seq )                        ! "*..$.*..7."
  [ ".0123456789" member? not ] find-all [ first ] map  ! { 0 3 5 }
;

: num-spans ( line -- seq )                                ! ".664.598.."
  >array [ over digit? [ nip ] [ 2drop f ] if ] map-index  ! { f 1 2 3 f 5 7 }
  { f } split harvest                                      ! { { 1 2 3 } { 5 7 } }
  [ [ first ] [ last ] bi 2array ] map                     ! { { 1 3 } { 5 7 } }
;

: adjacent? ( num-span symbol-indices -- ? )  ! { 1 3 } { 3 5 7 }
  swap [ first 1 - ] [ last 1 + ] bi [a,b]    ! { 3 5 7 } [0,4]
  '[ _ interval-contains? ] any?              ! t
;

: part-numbers ( line nearby-symbol-indices -- seq )  ! ".664.598.." { 0 5 6 }
  [ dup num-spans ] dip                               ! ".664.598.." { { 1 3 } { 5 7 } } { 0 5 6 }
  '[ _ adjacent? ] filter                             ! ".664.598.." { { 1 3 } { 5 7 } }
  swap '[ first2 1 + _ subseq string>number ] map     ! { 664 598 }
;

: part1 ( -- )
  "vocab:aoc-2023/day03/input.txt" utf8 file-lines             ! lines
  [ [ symbol-indices ] map ] keep                              ! lines-symbol-idxs lines
  [                                                            ! lines-symbol-idxs line line#
    pick swap [ 1 - ?nth-of ] [ nth-of ] [ 1 + ?nth-of ] 2tri  ! lines-symbol-idxs line prev-sym-idxs cur-sym-idxs next-sym-idxs
    3append part-numbers sum                                   ! lines-symbol-idxs line-parts-sum
  ] map-index sum nip .                                        ! total .
;

: star-indices ( line -- seq )          ! ".*.$.*...*"
  [ CHAR: * = ] find-all [ first ] map  ! { 1 5 9 }
;

: gears ( line prev-line next-line -- seq-of-pairs )        ! ".*.$*.*..." ".........." ".664.598..455"
  pick star-indices                                         ! ".*.$*.*..." ".........." ".664.598..455" { 1 4 6 }
  [ 1array '[ _ part-numbers ] [ 3dup ] dip tri@ 3append ]  ! ".*.$*.*..." ".........." ".664.598..455" { { 664 } { 664 598 } { 598 } }
  [ length 2 = ] map-filter [ 3drop ] dip                   ! { { 664 598 } }
;

: part2 ( -- )
  "vocab:aoc-2023/day03/input.txt" utf8 file-lines  ! lines
  dup [                                             ! lines line i
    pick swap [ 1 - ?nth-of ] [ 1 + ?nth-of ] 2bi   ! lines line prev next
    gears [ product ] map-sum                       ! lines line-ratio-sum
  ] map-index sum nip .                             ! total .
;

Language: C

Part 2 stumped me for a little bit, it wasn’t an obvious extension of part 1. Part 1 was about numbers (with one or more …) while part 2 worked from the symbols (with exactly two …). Going the other way would require more bookkeeping to avoid double counting.

And for the implementation: if you loop over the grid and check surrounding cells for digits you’d have to account for a bunch of cases, e.g. NW/N or N/NE being part of the same number or NW and NE being part of separate numbers. And you’d have to parse the numbers again. But building a graph or reference list of some sort is both unergonomic with C and not necessarily any simpler.

I ended up just writing out the cases, and honestly it didn’t turn out too bad.

GitHub link

int main(int argc, char **argv)
{
	static char G[GSZ][GSZ];
	static int N[GSZ][GSZ];
	int p1=0,p2=0, h=0, x,y, dx,dy, n=0,sym=0,r;
	
	for (h=0; fgets(&G[h+1][1], GSZ-1, stdin); h++)
		assert(h < GSZ);

	/*
	 * Pass 1: parse numbers and solve part 1. For every digit in
	 * G, the full number it is part of is stored in N.
	 */
	for (y=1; y<=h; y++)
	for (x=1; G[y][x]; x++)
		if (isdigit(G[y][x])) {
			n = n*10 + G[y][x]-'0';

			for (dy=-1; dy<2; dy++)
			for (dx=-1; dx<2; dx++)
				sym = sym || (x && y &&
				    G[y+dy][x+dx] != '.' &&
				    ispunct(G[y+dy][x+dx]));
		} else {
			for (dx=-1; isdigit(G[y][x+dx]); dx--)
				N[y][x+dx] = n;
			if (sym)
				p1 += n;
			n = sym = 0;
		}

	/*
	 * Pass 2: solve part 2 by finding all '*', then counting and
	 * multiplying adjecent numbers.
	 *
	 * Horizontal adjecency is trivial but vertical/diagonal has
	 * two situations: if there's a digit directly North of the '+',
	 * it must be a single number: NW and NE would connect to it.
	 * If N isn't a digit, digits in NW and NE belong to separate
	 * numbers.
	 */
	for (y=1; y<=h; y++)
	for (x=1; G[y][x]; x++) {
		if (G[y][x] != '*')
			continue;

		n = 0; r = 1;

		if (N[y][x-1]) { n++; r *= N[y][x-1]; }
		if (N[y][x+1]) { n++; r *= N[y][x+1]; }

		if (N[y-1][x]) { n++; r *= N[y-1][x]; } else {
			if (N[y-1][x-1]) { n++; r *= N[y-1][x-1]; }
			if (N[y-1][x+1]) { n++; r *= N[y-1][x+1]; }
		}

		if (N[y+1][x]) { n++; r *= N[y+1][x]; } else {
			if (N[y+1][x-1]) { n++; r *= N[y+1][x-1]; }
			if (N[y+1][x+1]) { n++; r *= N[y+1][x+1]; }
		}

		if (n == 2)
			p2 += r;
	}

	printf("%d %d\n", p1, p2);
	return 0;
}

Dart Solution

Holy moley, if this year is intended to be impervious to AI solution, it’s also working pretty well as a filter to this paltry Human Intelligence.

Find interesting symbols, look around for digits, and expand these into numbers. A dirty hacky solution leaning on a re-used Grid class. Not recommended.

late ListGrid grid;

Index look(Index ix, Index dir) {
  var here = ix;
  var next = here + dir;
  while (grid.isInBounds(next) && '1234567890'.contains(grid.at(next))) {
    here = next;
    next = here + dir;
  }
  return here;
}

/// Return start and end indices of a number at a point.
(Index, Index) expandNumber(Index ix) =>
    (look(ix, Grid.dirs['L']!), look(ix, Grid.dirs['R']!));

int parseNumber((Index, Index) e) => int.parse([
      for (var i = e.$1; i != e.$2 + Grid.dirs['R']!; i += Grid.dirs['R']!)
        grid.at(i)
    ].join());

/// Return de-duplicated positions of all numbers near the given symbols.
nearSymbols(Set syms) => [
      for (var ix in grid.indexes.where((i) => syms.contains(grid.at(i))))
        {
          for (var n in grid
              .near8(ix)
              .where((n) => ('1234567890'.contains(grid.at(n)))))
            expandNumber(n)
        }.toList()
    ];

part1(List lines) {
  grid = ListGrid([for (var e in lines) e.split('')]);
  var syms = lines
      .join('')
      .split('')
      .toSet()
      .difference('0123456789.'.split('').toSet());
  // Find distinct number locations near symbols and sum them.
  return {
    for (var ns in nearSymbols(syms))
      for (var n in ns) n
  }.map(parseNumber).sum;
}

part2(List lines) {
  grid = ListGrid([for (var e in lines) e.split('')]);
  // Look for _pairs_ of numbers near '*' and multiply them.
  var products = [
    for (var ns in nearSymbols({'*'}).where((e) => e.length == 2))
      ns.map(parseNumber).reduce((s, t) => s * t)
  ];
  return products.sum;
}

Python, used a number map to search positions near symbols.

https://github.com/massahud/advent-of-code-2023/blob/main/day03/day03.ipynb

[Rust] Harder one today, for part 1 I ended up getting stuck for a bit since I wasnt taking numbers at the end of lines into account and in part 2 I defined my gears vector in the wrong spot and spent a bit debugging that

use std::fs;

fn part1(input: String) -> u32 {
    let lines = input.lines().collect::>();
    let mut sum = 0;

    for i in 0..lines.len() {
        let mut num = 0;
        let mut valid = false;
        let chars = lines[i].chars().collect::>();

        for j in 0..chars.len() {
            let character = chars[j];
            let parts = ['*', '#', '+', '$', '/', '%', '=', '-', '&', '@'];

            if character.is_digit(10) {
                num = num * 10 + character.to_digit(10).unwrap();

                if i > 0 {
                    if parts.contains(&lines[i - 1].chars().collect::>()[j]) {
                        valid = true;
                    }

                    if j > 0 {
                        if parts.contains(&lines[i - 1].chars().collect::>()[j - 1]) {
                            valid = true;
                        }
                    }

                    if j < chars.len() - 1 {
                        if parts.contains(&lines[i - 1].chars().collect::>()[j + 1]) {
                            valid = true;
                        }
                    }
                }

                if i < lines.len() - 1 {
                    if parts.contains(&lines[i + 1].chars().collect::>()[j]) {
                        valid = true;
                    }

                    if j > 0 {
                        if parts.contains(&lines[i + 1].chars().collect::>()[j - 1]) {
                            valid = true;
                        }
                    }

                    if j < chars.len() - 1 {
                        if parts.contains(&lines[i + 1].chars().collect::>()[j + 1]) {
                            valid = true;
                        }
                    }
                }

                if j > 0 {
                    if parts.contains(&lines[i].chars().collect::>()[j - 1]) {
                        valid = true;
                    }
                }

                if j < chars.len() - 1 {
                    if parts.contains(&lines[i].chars().collect::>()[j + 1]) {
                        valid = true;
                    }
                }
            }
            else {
                if valid == true {
                    sum += num;
                }

                num = 0;
                valid = false;
            }

            if j == chars.len() - 1 {
                if valid == true {
                    sum += num;
                }

                num = 0;
                valid = false;
            }
        }
    }

    return sum;
}

fn part2(input: String) -> u32 {
    let lines = input.lines().collect::>();
    let mut gears: Vec<(usize, usize, u32)> = Vec::new();
    let mut sum = 0;

    for i in 0..lines.len() {
        let mut num = 0;
        let chars = lines[i].chars().collect::>();
        let mut pos: (usize, usize) = (0, 0);
        let mut valid = false;

        for j in 0..chars.len() {
            let character = chars[j];
            let parts = ['*'];

            if character.is_digit(10) {
                num = num * 10 + character.to_digit(10).unwrap();

                if i > 0 {
                    if parts.contains(&lines[i - 1].chars().collect::>()[j]) {
                        valid = true;
                        pos = (i - 1, j);
                    }

                    if j > 0 {
                        if parts.contains(&lines[i - 1].chars().collect::>()[j - 1]) {
                            valid = true;
                            pos = (i - 1, j - 1);
                        }
                    }

                    if j < chars.len() - 1 {
                        if parts.contains(&lines[i - 1].chars().collect::>()[j + 1]) {
                            valid = true;
                            pos = (i - 1, j + 1);
                        }
                    }
                }

                if i < lines.len() - 1 {
                    if parts.contains(&lines[i + 1].chars().collect::>()[j]) {
                        valid = true;
                        pos = (i + 1, j);
                    }

                    if j > 0 {
                        if parts.contains(&lines[i + 1].chars().collect::>()[j - 1]) {
                            valid = true;
                            pos = (i + 1, j - 1);
                        }
                    }

                    if j < chars.len() - 1 {
                        if parts.contains(&lines[i + 1].chars().collect::>()[j + 1]) {
                            valid = true;
                            pos = (i + 1, j + 1);
                        }
                    }
                }

                if j > 0 {
                    if parts.contains(&lines[i].chars().collect::>()[j - 1]) {
                        valid = true;
                        pos = (i, j - 1);
                    }
                }

                if j < chars.len() - 1 {
                    if parts.contains(&lines[i].chars().collect::>()[j + 1]) {
                        valid = true;
                        pos = (i, j + 1);
                    }
                }
            }
            else {
                if valid == true {
                    let mut current_gear = false;
                    
                    for gear in &gears {
                        if gear.0 == pos.0 && gear.1 == pos.1 {
                            sum += num * gear.2;
                            current_gear = true;
                            break;
                        }
                    }
                    
                    if !current_gear {
                        let tuple_to_push = (pos.0.clone(), pos.1.clone(), num.clone());
                        gears.push((pos.0.clone(), pos.1.clone(), num.clone()));
                    }
                }

                num = 0;
                valid = false;
            }

            if j == chars.len() - 1 {
                if valid == true {
                    let mut current_gear = false;
                    
                    for gear in &gears {
                        if gear.0 == pos.0 && gear.1 == pos.1 {
                            sum += num * gear.2;
                            current_gear = true;
                            break;
                        }
                    }
                    
                    if !current_gear {
                        let tuple_to_push = (pos.0.clone(), pos.1.clone(), num.clone());
                        gears.push((pos.0.clone(), pos.1.clone(), num.clone()));
                    }
                }

                num = 0;
                valid = false;
            }
        }
    }

    return sum;
}

fn main() {
    let input = fs::read_to_string("data/input.txt").unwrap();

    println!("{}", part1(input.clone()));
    println!("{}", part2(input.clone()));
}

Code Link

Did this in Odin

Here’s a tip: if you are using a language / standard library that doesn’t have a set, you can mimic it with a map from your key to a nullary (in this case an empty struct)

formatted code

package day3

import "core:fmt"
import "core:strings"
import "core:unicode"
import "core:strconv"

flood_get_num :: proc(s: string, i: int) -> (parsed: int, pos: int) {
    if !unicode.is_digit(rune(s[i])) do return -99999, -1

    pos = strings.last_index_proc(s[:i+1], proc(r:rune)->bool{return !unicode.is_digit(r)})
    pos += 1

    ok: bool
    parsed, ok = strconv.parse_int(s[pos:])

    return parsed, pos
}

p1 :: proc(input: []string) {
    // wow what a gnarly type
    foundNumSet := make(map[[2]int]struct{})
    defer delete(foundNumSet)

    total := 0

    for y in 0..