Table of content

What is this :grey_question:

The rules of the game are explained in my original post.

29th Challenge

Challenge

Today I’m solving last year’s AoC day 3 2020 using rust macros whenever possible.

Solution :white_check_mark:

This is the result, it calculates the example correctly, but not the second challenge’s personalized input.. I will have to check tomrrow what is going on.

	fn main() {
	    println!("product: {}",slope_product!(INPUT,0,1,2,3,4));
	}


	#[macro_export]
	macro_rules! slope_product {
	    ( $input:expr,$( $x:expr ),* ) => {
	        {
	            let mut prod = 1;
	            $(
	                println!("slope: {}",slope!($x,$input));
	                prod*=slope!($x,$input);
	            )*
	            prod
	        }
	    };
	}

	#[macro_export]
	macro_rules! slope {
	    (  $slope:expr,$input:expr ) => {
	        {
	            $input.lines()
	                    .enumerate()
	                    .filter(|x| {is_tree!($slope,x.0,x.1)})
	                    .count()
	        }
	    };
	}

	#[macro_export]
	macro_rules! is_tree {
	    (4,$i:expr,$s:expr) => {
	        {
	            match $i % 2 {
	                0 => is_tree!(0,$i,$s),
	                _ => false
	            }
	        }
	    };
	    ($slope:expr,$i:expr,$s:expr) => {
	        {
	            $s.chars().nth(($i*(1+$slope*2))%$s.chars().count()).unwrap() == '#'
	        }
	    };

	}

	const INPUT: &str ="..##.........##.........##.........##.........##.........##.......
	#...#...#..#...#...#..#...#...#..#...#...#..#...#...#..#...#...#..
	.#....#..#..#....#..#..#....#..#..#....#..#..#....#..#..#....#..#.
	..#.#...#.#..#.#...#.#..#.#...#.#..#.#...#.#..#.#...#.#..#.#...#.#
	.#...##..#..#...##..#..#...##..#..#...##..#..#...##..#..#...##..#.
	..#.##.......#.##.......#.##.......#.##.......#.##.......#.##.....
	.#.#.#....#.#.#.#....#.#.#.#....#.#.#.#....#.#.#.#....#.#.#.#....#
	.#........#.#........#.#........#.#........#.#........#.#........#
	#.##...#...#.##...#...#.##...#...#.##...#...#.##...#...#.##...#...
	#...##....##...##....##...##....##...##....##...##....##...##....#
	.#..#...#.#.#..#...#.#.#..#...#.#.#..#...#.#.#..#...#.#.#..#...#.#
	";

To see the full source see github and see the live demo in playground.