AoC2021/src/day02.rs

use crate::Day;
use anyhow::Result;

pub struct Day02(Vec<Instruction>);

enum Instruction {
    Forward(i32),
    Down(i32),
    Up(i32),
}

impl Day for Day02 {
    fn init(content: String) -> Result<Self> {
        let lines = content.lines().map(str_to_instr).collect::<Result<Vec<Instruction>>>()?;
        Ok(Self(lines))
    }

    fn part1(&self) -> Result<String> {
        let mut depth = 0;
        let mut fw = 0;
        for i in &self.0 {
            match i {
                Instruction::Forward(n) => fw += n,
                Instruction::Down(n) => depth += n,
                Instruction::Up(n) => depth -= n,
            }
        }
        Ok(format!("{}", depth * fw))
    }

    fn part2(&self) -> Result<String> {
        let mut depth = 0;
        let mut fw = 0;
        let mut aim = 0;
        for i in &self.0 {
            match i {
                Instruction::Forward(n) => {
                    fw += n;
                    depth += aim * n;
                }
                Instruction::Down(n) => aim += n,
                Instruction::Up(n) => aim -= n,
            }
        }
        Ok(format!("{}", depth * fw))
    }
}

fn str_to_instr(s: &str) -> Result<Instruction> {
    let v = s.split(' ').collect::<Vec<&str>>();
    let name = v[0];
    let height = v[1].parse()?;
    match name {
        "forward" => Ok(Instruction::Forward(height)),
        "up" => Ok(Instruction::Up(height)),
        "down" => Ok(Instruction::Down(height)),
        _ => Err(anyhow::Error::msg("This is not a valid direction!"))
    }
}

#[cfg(test)]
mod tests {
    use crate::day02::Day02;
    use crate::day::Day;
    use crate::day_tests;
    use super::Result;

    const D: &str = r"forward 5
down 5
forward 8
up 3
down 8
forward 2";

    #[test]
    fn part1_test() -> Result<()> {
        let d2 = Day02::init(String::from(D))?;
        Ok(assert_eq!("150", d2.part1()?))
    }

    #[test]
    fn part2_test() -> Result<()> {
        let d2 = Day02::init(String::from(D))?;
        Ok(assert_eq!("900", d2.part2()?))
    }

    day_tests!(Day02, "02", "1524750", "1592426537");
}