(2017, 19) => year_2017::day19::run(inputs::read(year, day)),

use std::collections::HashMap;

pub fn run(input: Vec<String>) {

let part1 = solve(input.clone()).0;

println!("part 1: {}", part1);

assert_eq!(part1, "RYLONKEWB");

let part2 = solve(input.clone()).1;

println!("part 2: {}", part2);

assert_eq!(part2, 16016);

fn solve(input: Vec<String>) -> (String, u64) {

let mut grid = HashMap::new();

// Parse the input

for y in 0..input.len() {

for x in 0..input[y].len() {

grid.insert((x as i64, y as i64), input[y].chars().nth(x).unwrap());

}

}

// find the starting position

let mut pos_y: i64 = 0;

let mut pos_x: i64 = input[0].chars().enumerate().find(|&(_, c)| c == '|').unwrap().0 as i64;

let mut dir = 0;

let dirs = [(0, 1), (-1, 0), (0, -1), (1, 0)];

// move around the grid until we are done

let mut letters = String::new();

let mut steps = 0;

loop {

let c = *grid.entry((pos_x, pos_y)).or_insert(' ');

match c {

'A'...'Z' => {

letters.push(c);

}

'|' | '-' => {}

'+' => {

// we either need to go dir+1 or dir-1

let c1 = *grid.entry((pos_x + dirs[(dir + 1) % 4].0, pos_y + dirs[(dir + 1) % 4].1))

.or_insert(' ');

let c2 = *grid.entry((pos_x + dirs[(dir + 3) % 4].0, pos_y + dirs[(dir + 3) % 4].1))

.or_insert(' ');

match (c1, c2) {

(' ', ' ') => panic!("both directions result in space"),

(_, ' ') => {

dir = (dir + 1) % 4;

}

(' ', _) => {

dir = (dir + 3) % 4;

}

_ => panic!("neither direction results in a space"),

}

}

' ' => {

// we are done

break;

}

_ => panic!("unknown char: {}", c as u8),

}

pos_x += dirs[dir].0;

pos_y += dirs[dir].1;

steps += 1;

}

return (letters, steps);

pub mod day19;