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|
use nom::{
branch::alt,
character::complete::{char, line_ending},
combinator::{map, value},
multi::{many1, separated_list1},
IResult,
};
use std::{collections::BTreeMap, fs};
fn main() -> Result<(), Box<dyn std::error::Error>> {
let input = fs::read_to_string("inputs/day_14.txt")?;
let rock_field = RockField::parser(&input).unwrap().1;
{
let mut north_rock_field = rock_field.clone();
north_rock_field.tilt_north();
dbg!(&north_rock_field.north_load());
}
{
let mut spin_rock_field = rock_field.clone();
let mut last_east = BTreeMap::new();
let mut i = 0;
let target = 1000000000;
while i < target {
spin_rock_field.tilt_north();
spin_rock_field.tilt_west();
spin_rock_field.tilt_south();
spin_rock_field.tilt_east();
if let Some(last_i) = last_east.get(&spin_rock_field) {
let interval = i - last_i;
// relying on integer division to round down here, want to add
// interval as many times as possible without going over target.
i += ((target - i) / interval) * interval;
} else {
last_east.insert(spin_rock_field.clone(), i);
}
i += 1;
}
dbg!(&spin_rock_field.north_load());
}
Ok(())
}
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
struct RockField(Vec<Vec<Rock>>);
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
enum Rock {
Rounded,
Cubed,
None,
}
impl RockField {
fn parser(input: &str) -> IResult<&str, Self> {
map(separated_list1(line_ending, many1(Rock::parser)), RockField)(input)
}
fn tilt_north(&mut self) {
for y in 0..self.0.len() {
for x in 0..self.0[y].len() {
if self.0[y][x] == Rock::Rounded {
let new_y = (0..y)
.rev()
.take_while(|new_y| self.0[*new_y][x] == Rock::None)
.last();
if let Some(new_y) = new_y {
self.0[new_y][x] = Rock::Rounded;
self.0[y][x] = Rock::None;
}
}
}
}
}
fn tilt_west(&mut self) {
for x in 0..self.0[0].len() {
for y in 0..self.0.len() {
if self.0[y][x] == Rock::Rounded {
let new_x = (0..x)
.rev()
.take_while(|new_x| self.0[y][*new_x] == Rock::None)
.last();
if let Some(new_x) = new_x {
self.0[y][new_x] = Rock::Rounded;
self.0[y][x] = Rock::None;
}
}
}
}
}
fn tilt_south(&mut self) {
for y in (0..self.0.len()).rev() {
for x in 0..self.0[y].len() {
if self.0[y][x] == Rock::Rounded {
let new_y = (y + 1..self.0.len())
.take_while(|new_y| self.0[*new_y][x] == Rock::None)
.last();
if let Some(new_y) = new_y {
self.0[new_y][x] = Rock::Rounded;
self.0[y][x] = Rock::None;
}
}
}
}
}
fn tilt_east(&mut self) {
for x in (0..self.0[0].len()).rev() {
for y in 0..self.0.len() {
if self.0[y][x] == Rock::Rounded {
let new_x = (x + 1..self.0[0].len())
.take_while(|new_x| self.0[y][*new_x] == Rock::None)
.last();
if let Some(new_x) = new_x {
self.0[y][new_x] = Rock::Rounded;
self.0[y][x] = Rock::None;
}
}
}
}
}
fn north_load(&self) -> usize {
self.0
.iter()
.enumerate()
.map(|(y, row)| {
row.iter().filter(|r| **r == Rock::Rounded).count() * (self.0.len() - y)
})
.sum()
}
}
impl Rock {
fn parser(input: &str) -> IResult<&str, Self> {
alt((
value(Rock::Rounded, char('O')),
value(Rock::Cubed, char('#')),
value(Rock::None, char('.')),
))(input)
}
}
|
