Table of content

What is this
29th Challenge
- Challenge
- Solution

What is this

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

30th Challenge

Challenge

Today I’m solving last year’s AoC day 3 2020 using rust macros whenever possible. In yesterday’s solution there was a small bug in my code, I will try to solve that today.

Solution

The issue was with slope number four. I repeated the challenge for just number four

    println!("{}",INPUT.lines()
                .enumerate()
                .filter(|x| { (x.0%2 == 0) && (x.1.chars().nth((x.0/2)%31).unwrap() == '#')})
                .count());

From this huntch I was able to solve the issue.

	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 {
	    ($slope:expr,$i:expr,$s:expr) => {
	        {
	            match $slope {
	                4 => {(($i%2)==0) && $s.chars().nth(($i/2)%$s.chars().count()).unwrap() == '#'},
	                _ => $s.chars().nth(($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.