Day 3: Gear Ratios
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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/
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I like it, it’s simple and to the point. I’ve learned that one of the most helpful things to do when solving these puzzles is to not make it more complicated than it needs to be, and you certainly succeeded better at that today than I did.
My solution for day 1 part 1 was simple and to the point. The other ones are getting increasingly less so. You’re right that sometimes it’s best not to get too fancy, but I think soon I may have to break out such advanced programming techniques as “functions” and maybe “objects”, instead of writing increasingly convoluted piles of nested loops. xD
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: [email protected]
nested loops
This is the way
That was not fun to solve. Lots of ugly code. This is a less ugly second version. Language: 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:-
Rust
I’ve been using Regexes for every day so far, this time it helped in finding numbers along with their start and end position in a line. For the second part I mostly went with the approach of part 1 which was to look at all numbers and then figure out if it has a part symbol around it. Only in part 2 I saved all numbers next to a gear
*
in a hash table that maps each gear position to a list of adjacent numbers. Then in the end I can just look at all gears with exactly 2 numbers attached.Also it has to be said, multiplying two numbers is the exact opposite of getting their ratio!
My Python solution for part 1 and part 2. I really practice my regex skills.
spoiler
#!/usr/bin/python3 import re value_re = '(\d+)' symbol_re = '[^\d.]' gear_re = '(\*)' def main(): input = list() with open("input.txt", 'r') as in_file: for line in in_file: input.append(line.strip('\n')) length = len(input) width = len(input[0]) value_sum = 0 for idx, line in enumerate(input): for match in re.finditer(value_re, line): for line_mask in input[max(idx - 1, 0):min(idx + 2, length)]: valid_chars = line_mask[max(match.span()[0] - 1, 0):min(match.span()[1] + 1, width)] if re.search(symbol_re, valid_chars): value_sum += int(match[0]) break print(f"Value sum = {value_sum}") gear_ratio = 0 for idx, line in enumerate(input): for match in re.finditer(gear_re, line): valid_lines = input[max(idx - 1, 0):min(idx + 2, length)] min_range = max(match.span()[0] - 1, 0) max_range = min(match.span()[1], width) num_of_adjacent = 0 temp_gear_ratio = 1 for valid_line in valid_lines: for match in re.finditer(value_re, valid_line): if match.span()[0] in range(min_range,max_range + 1) or match.span()[1] - 1 in range(min_range,max_range + 1): num_of_adjacent += 1 temp_gear_ratio *= int(match[0]) if num_of_adjacent == 2: gear_ratio += temp_gear_ratio print(f"Gear ratio = {gear_ratio}") if __name__ == '__main__': main()
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 🦀
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))); } }
just more parsing problems
deleted by creator
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!
One solution for both
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])); } }
Python, used a number map to search positions near symbols.
https://github.com/massahud/advent-of-code-2023/blob/main/day03/day03.ipynb
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; }
what language is this? I don’t recognize it
Sorry, it’s Dart. I’ll update it.
Factor on github (with comments and imports):
: symbol-indices ( line -- seq ) [ ".0123456789" member? not ] find-all [ first ] map ; : num-spans ( line -- seq ) >array [ over digit? [ nip ] [ 2drop f ] if ] map-index { f } split harvest [ [ first ] [ last ] bi 2array ] map ; : adjacent? ( num-span symbol-indices -- ? ) swap [ first 1 - ] [ last 1 + ] bi [a,b] '[ _ interval-contains? ] any? ; : part-numbers ( line nearby-symbol-indices -- seq ) [ dup num-spans ] dip '[ _ adjacent? ] filter swap '[ first2 1 + _ subseq string>number ] map ; : part1 ( -- ) "vocab:aoc-2023/day03/input.txt" utf8 file-lines [ [ symbol-indices ] map ] keep [ pick swap [ 1 - ?nth-of ] [ nth-of ] [ 1 + ?nth-of ] 2tri 3append part-numbers sum ] map-index sum nip . ; : star-indices ( line -- seq ) [ CHAR: * = ] find-all [ first ] map ; : gears ( line prev-line next-line -- seq-of-pairs ) pick star-indices [ 1array '[ _ part-numbers ] [ 3dup ] dip tri@ 3append ] [ length 2 = ] map-filter [ 3drop ] dip ; : part2 ( -- ) "vocab:aoc-2023/day03/input.txt" utf8 file-lines dup [ pick swap [ 1 - ?nth-of ] [ 1 + ?nth-of ] 2bi gears [ product ] map-sum ] map-index sum nip . ;
[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
Code
(lemmy removes some chars, all chars are in code link)
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())); }
Ruby
My goodness I struggled today. https://github.com/snowe2010/advent-of-code/blob/master/ruby_aoc/2023/day03/day03.rb
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: [email protected]
Had an off-by-one error that took me a while to find