Advent of Code 2021 - Day 2: Dive!

dive.rs

fn plot_course(instructions: &[&str]) -> i64 {
    let mut pos = 0;
    let mut depth = 0;

    for &instruction in instructions {
        let mut parts = instruction.split_whitespace();
        let direction = parts.next().unwrap();
        let units = parts.next().unwrap().parse::<i64>().unwrap();

        match direction {
            "forward" => pos += units,
            "down" => depth += units,
            "up" => depth -= units,
            _ => panic!("Unknown direction: {}", direction),
        }
    }

    pos * depth
}

fn plot_course_with_aim(instructions: &[&str]) -> i64 {
    let mut pos = 0;
    let mut depth = 0;
    let mut aim = 0;

    for &instruction in instructions {
        let mut parts = instruction.split_whitespace();
        let direction = parts.next().unwrap();
        let units = parts.next().unwrap().parse::<i64>().unwrap();

        match direction {
            "forward" => {
                pos += units;
                depth += units * aim;
            }
            "down" => aim += units,
            "up" => aim -= units,
            _ => panic!("Unknown direction: {}", direction),
        }
    }

    pos * depth
}