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use std::{
fmt::Display,
ops::{Deref, DerefMut},
str::FromStr,
};
use anyhow::{Context, Result};
use crate::{Problem, Solution};
#[derive(Debug)]
struct Procedure(Vec<Step>);
impl Procedure {
fn run(self, mut stacks: Stacks, in_order: bool) -> Result<Stacks> {
for step in self.0 {
let mut move_stack = Vec::new();
for _ in 0..step.count {
let cargo = stacks[step.from - 1]
.pop()
.ok_or_else(|| anyhow::anyhow!("ran out of cargo"))?;
move_stack.push(cargo)
}
if in_order {
move_stack.reverse()
}
stacks[step.to - 1].append(&mut move_stack);
}
Ok(stacks)
}
}
impl FromStr for Procedure {
type Err = anyhow::Error;
fn from_str(s: &str) -> Result<Self> {
let mut procedure = Procedure(Vec::new());
for (linenr, step) in s.lines().enumerate() {
procedure.push(
step.parse()
.context(format!("Error in procedure step {}: '{}'", linenr, step))?,
)
}
Ok(procedure)
}
}
impl Deref for Procedure {
type Target = Vec<Step>;
fn deref(&self) -> &Self::Target {
&self.0
}
}
impl DerefMut for Procedure {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.0
}
}
#[derive(Debug)]
struct Step {
count: usize,
from: usize,
to: usize,
}
impl FromStr for Step {
type Err = anyhow::Error;
fn from_str(s: &str) -> Result<Self> {
let mut items = s.split_whitespace();
Ok(Self {
count: items.next_chunk::<2>().unwrap().last().unwrap().parse()?,
from: items.next_chunk::<2>().unwrap().last().unwrap().parse()?,
to: items.next_chunk::<2>().unwrap().last().unwrap().parse()?,
})
}
}
#[derive(Debug)]
struct Stacks(Vec<Vec<char>>);
impl Stacks {
fn top(mut self) -> String {
self.iter_mut().fold(
"".to_owned(),
|mut acc: String, s: &mut std::vec::Vec<char>| {
if let Some(c) = s.pop() {
acc.push(c)
}
acc
},
)
}
}
impl Deref for Stacks {
type Target = Vec<Vec<char>>;
fn deref(&self) -> &Self::Target {
&self.0
}
}
impl DerefMut for Stacks {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.0
}
}
impl FromStr for Stacks {
type Err = anyhow::Error;
fn from_str(s: &str) -> Result<Self> {
let mut stacks = Self(Vec::new());
for line in s.lines().rev().skip(1) {
let mut chars = line.chars().skip(1).enumerate();
loop {
let (stack, cargo) = match chars.next() {
Some((_, '[' | ']' | ' ')) => continue,
Some((index, c)) => (index / 4, c),
None => break,
};
if stacks.len() < stack + 1 {
stacks.push(Vec::new())
}
stacks[stack].push(cargo)
}
}
Ok(stacks)
}
}
impl Display for Stacks {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
let Some(max_len) = self.0.iter().map(|v| v.len()).max() else {
return Ok(())
};
for i in (0..max_len).rev() {
let mut cargos = Vec::new();
for stack in &self.0 {
let cargo = match stack.get(i) {
Some(c) => format!("[{}]", c),
None => " ".to_owned(),
};
cargos.push(cargo);
}
writeln!(f, "{}", cargos.join(" "))?
}
Ok(())
}
}
pub struct Day5;
impl Problem for Day5 {
const DAY: u8 = 5;
const INPUT: &'static str = include_str!("../input/day_5.txt");
}
impl Solution for Day5 {
type Answer1 = String;
type Answer2 = String;
fn part_1(input: &str) -> Result<Self::Answer1, anyhow::Error> {
let (stacks, procedure) = input.split_once("\n\n").unwrap();
let stacks = Stacks::from_str(stacks)?;
let procedure = Procedure::from_str(procedure)?;
Ok(procedure.run(stacks, false)?.top())
}
fn part_2(input: &str) -> Result<Self::Answer2, anyhow::Error> {
let (stacks, procedure) = input.split_once("\n\n").unwrap();
let stacks = Stacks::from_str(stacks)?;
let procedure = Procedure::from_str(procedure)?;
Ok(procedure.run(stacks, true)?.top())
}
}
#[cfg(test)]
mod tests {
use super::*;
const TEST_INPUT: &str = indoc::indoc! {r#"
[D]
[N] [C]
[Z] [M] [P]
1 2 3
move 1 from 2 to 1
move 3 from 1 to 3
move 2 from 2 to 1
move 1 from 1 to 2
"#};
#[test]
fn test_part_1_example() -> Result<()> {
Ok(assert_eq!("CMZ", Day5::part_1(TEST_INPUT)?))
}
#[test]
fn test_part_2_example() -> Result<()> {
Ok(assert_eq!("MCD", Day5::part_2(TEST_INPUT)?))
}
}
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