aoc22/day05/src/main.rs

#![feature(iter_next_chunk)]
use std::collections::VecDeque;

const OFFSET: usize = 4;

enum MachineType {
    Type9000,
    Type9001,
}

fn main() {
    let f = std::fs::read_to_string("/dev/stdin").unwrap();
    let (crates, instructions) = f.split_once("\n\n").unwrap();
    let (crates, instructions) = (crates.lines(), instructions.lines());

    let mut stacks: Vec<VecDeque<&str>> =
        vec![VecDeque::new(); (f.lines().next().unwrap().len() / 4) + 1];

    for crate_str in crates {
        for i in (1..crate_str.len()).step_by(OFFSET) {
            if let Some(crate_label) = crate_str.get(i..i + 1) {
                if !crate_label.chars().next().unwrap().is_alphabetic() {
                    continue;
                }
                let vee = stacks.get_mut(i / 4).unwrap();
                vee.push_front(crate_label);
            }
        }
    }

    let (mut reset_stacks, reset_instructions) = (stacks.clone(), instructions.clone());

    solve(instructions, &mut stacks, MachineType::Type9000);
    solve(reset_instructions, &mut reset_stacks, MachineType::Type9001);
}

fn solve(instructions: core::str::Lines, stacks: &mut [VecDeque<&str>], machine_type: MachineType) {
    for instruction in instructions {
        if let Ok([amount, source, dest]) = instruction
            .split_whitespace()
            .filter_map(|n| n.parse::<usize>().ok())
            .next_chunk()
        {
            let mut temp = VecDeque::new();
            let source_stack = stacks.get_mut(source - 1).unwrap();
            for _ in 0..amount {
                temp.push_front(source_stack.pop_back().unwrap());
            }
            let dest_stack = stacks.get_mut(dest - 1).unwrap();
            match machine_type {
                MachineType::Type9000 => {
                    for _ in 0..amount {
                        dest_stack.push_back(temp.pop_back().unwrap());
                    }
                }
                MachineType::Type9001 => {
                    if amount == 1 {
                        dest_stack.push_back(temp.pop_back().unwrap());
                    } else {
                        dest_stack.append(&mut temp);
                    }
                }
            }
        }
    }
    if matches!(machine_type, MachineType::Type9000) {
        print!("P1: ");
    } else {
        print!("P2: ");
    }
    for stack in stacks.iter_mut() {
        print!("{}", stack.pop_back().unwrap());
    }
    println!();
}