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|
use nom::{
branch::alt,
bytes::complete::tag,
character::complete::{
anychar, char as nom_char, line_ending, not_line_ending, u32 as nom_u32,
},
combinator::map,
multi::separated_list1,
sequence::tuple,
IResult,
};
use std::fs;
fn main() -> Result<(), Box<dyn std::error::Error>> {
let input = fs::read_to_string("inputs/day_5.txt")?;
let state = CraneState::parser(&input).unwrap().1;
let mut state_part_1 = state.clone();
while !state_part_1.done() {
state_part_1.process_next_instruction(false);
}
dbg!(state_part_1.read_top_row());
let mut state_part_2 = state.clone();
while !state_part_2.done() {
state_part_2.process_next_instruction(true);
}
dbg!(state_part_2.read_top_row());
Ok(())
}
#[derive(Debug, PartialEq, Eq, Clone)]
struct CraneState {
towers: Vec<Tower>,
instructions: Vec<Instruction>,
}
#[derive(Debug, Default, PartialEq, Eq, Clone)]
struct Tower {
crates: Vec<char>,
}
#[derive(Debug, PartialEq, Eq, Clone)]
struct Instruction {
number: usize,
src: usize,
dest: usize,
}
impl CraneState {
fn parser(input: &str) -> IResult<&str, CraneState> {
let single_crate = alt((
map(tuple((tag("["), anychar, tag("]"))), |(_, c, _)| Some(c)),
map(tag(" "), |_| None),
));
let crate_row = separated_list1(nom_char(' '), single_crate);
map(
tuple((
separated_list1(line_ending, crate_row),
line_ending,
not_line_ending,
line_ending,
line_ending,
separated_list1(line_ending, Instruction::parser),
)),
|(crate_rows, _, _, _, _, mut instructions)| {
let mut towers = Vec::new();
for row in &crate_rows {
for (i, c) in row
.iter()
.enumerate()
.filter_map(|(i, c)| c.map(|some_c| (i, some_c)))
{
while i >= towers.len() {
towers.push(Tower::default());
}
towers[i].crates.push(c);
}
}
for tower in &mut towers {
tower.crates.reverse();
}
instructions.reverse();
CraneState {
towers,
instructions,
}
},
)(input)
}
fn process_next_instruction(&mut self, maintain_order: bool) {
let Some(instruction) = self.instructions.pop() else {
return
};
let mut to_move = Vec::new();
for _ in 0..instruction.number {
let Some(crate_to_move) = self.towers[instruction.src].crates.pop() else {
panic!("Invalid puzzle input: failed to get crate");
};
to_move.push(crate_to_move);
}
if maintain_order {
to_move.reverse();
}
for crate_to_move in to_move {
self.towers[instruction.dest].crates.push(crate_to_move);
}
}
fn done(&self) -> bool {
self.instructions.len() == 0
}
fn read_top_row(&self) -> String {
let mut res = String::new();
for tower in &self.towers {
if let Some(top) = tower.crates.last() {
res.push(*top);
}
}
res
}
}
impl Instruction {
fn parser(input: &str) -> IResult<&str, Instruction> {
map(
tuple((
tag("move "),
nom_u32,
tag(" from "),
nom_u32,
tag(" to "),
nom_u32,
)),
|(_, number, _, src, _, dest)| Instruction {
number: number as usize,
src: (src - 1) as usize,
dest: (dest - 1) as usize,
},
)(input)
}
}
|
