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use std::collections::HashMap;
fn main() {
let input = advent::read_file(3);
println!("3a: {}", houses_visited(&input));
println!("3b: {}", houses_visited_robo(&input));
}
fn new_pos(pos: (i32, i32), c: char) -> (i32, i32) {
match c {
'v' => (pos.0, pos.1 - 1),
'^' => (pos.0, pos.1 + 1),
'<' => (pos.0 - 1, pos.1),
'>' => (pos.0 + 1, pos.1),
_ => panic!("invalid character"),
}
}
fn houses_visited(input: &str) -> usize {
let mut map = HashMap::new();
let mut pos = (0, 0);
map.insert(pos, 1);
for c in input.chars() {
pos = new_pos(pos, c);
let count = map.entry(pos).or_insert(0);
*count += 1;
}
map.keys().len()
}
fn houses_visited_robo(input: &str) -> usize {
let mut map = HashMap::new();
let mut pos_santa = (0, 0);
let mut pos_robo = (0, 0);
map.insert(pos_santa, 2);
for c in input.chars().step_by(2) {
pos_santa = new_pos(pos_santa, c);
let count = map.entry(pos_santa).or_insert(0);
*count += 1;
}
for c in input.chars().skip(1).step_by(2) {
pos_robo = new_pos(pos_robo, c);
let count = map.entry(pos_robo).or_insert(0);
*count += 1;
}
map.keys().len()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
assert_eq!(houses_visited(">"), 2);
assert_eq!(houses_visited("^>v<"), 4);
assert_eq!(houses_visited("^v^v^v^v^v"), 2);
}
#[test]
fn test_robo() {
assert_eq!(houses_visited_robo("^v"), 3);
assert_eq!(houses_visited_robo("^>v<"), 3);
assert_eq!(houses_visited_robo("^v^v^v^v^v"), 11);
}
}
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