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use advent_of_code::prelude::*;
pub enum Command {
Forward(i64),
Down(i64),
Up(i64),
}
pub fn parse(fh: File) -> Result<impl Iterator<Item = Command>> {
Ok(parse::raw_lines(fh).map(|line| {
if let Some(n) = line.strip_prefix("forward ") {
Command::Forward(n.parse().unwrap())
} else if let Some(n) = line.strip_prefix("down ") {
Command::Down(n.parse().unwrap())
} else if let Some(n) = line.strip_prefix("up ") {
Command::Up(n.parse().unwrap())
} else {
panic!("couldn't parse line: {}", line);
}
}))
}
pub fn part1(commands: impl Iterator<Item = Command>) -> Result<i64> {
let mut horizontal = 0;
let mut vertical = 0;
for command in commands {
match command {
Command::Forward(n) => {
horizontal += n;
}
Command::Down(n) => {
vertical += n;
}
Command::Up(n) => {
vertical -= n;
}
}
}
Ok(horizontal * vertical)
}
pub fn part2(commands: impl Iterator<Item = Command>) -> Result<i64> {
let mut aim = 0;
let mut horizontal = 0;
let mut vertical = 0;
for command in commands {
match command {
Command::Forward(n) => {
horizontal += n;
vertical += aim * n;
}
Command::Down(n) => {
aim += n;
}
Command::Up(n) => {
aim -= n;
}
}
}
Ok(horizontal * vertical)
}
#[test]
fn test() {
assert_eq!(
part1(parse(parse::data(2021, 2).unwrap()).unwrap()).unwrap(),
1694130
);
assert_eq!(
part2(parse(parse::data(2021, 2).unwrap()).unwrap()).unwrap(),
1698850445
);
}
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