aoc 2022 day05

day05.rs

fn main() {
    let input = include_str!("day05_input.txt");
    let lines = input.split("\n").collect::<Vec<&str>>();

    // find where the file switches from stacks to instructions
    let mut split = 0;
    for (i, line) in lines.iter().enumerate() {
        if line.is_empty() {
            split = i;
        }
    }

    // note: hardcoded size.
    let mut stacks = vec![vec![]; 9];

    // build stacks
    for i in (0..=(split - 2)).rev() {
        let line = lines[i];
        for j in (0..line.len()).step_by(4) {
            let slot = &line[j + 1..j + 2];
            if slot == " " {
            } else {
                let stack = &mut stacks[(j / 4)];
                stack.push(slot);
            }
        }
    }

    for line in &lines[split + 1..lines.len()] {
        let words = line.split(" ").collect::<Vec<&str>>();
        let num: usize = words[1].parse().unwrap();
        let mut from: usize = words[3].parse().unwrap();
        from -= 1;
        let mut to: usize = words[5].parse().unwrap();
        to -= 1;

        // part 1
        // for _ in 0..num {
        //     let elem = stacks[from].pop().unwrap();
        //     stacks[to].push(elem);
        // }

        // part 2
        let mut buf = vec![];
        for _ in 0..num {
            let elem = stacks[from].pop().unwrap();
            buf.push(elem);
        }
        buf.reverse();
        stacks[to].append(&mut buf);
    }

    // print answer
    for i in 0..stacks.len() {
        eprint!("{}", stacks[i].pop().unwrap());
    }
    eprintln!();
}