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|
use nom::{
branch::alt,
bytes::complete::tag,
character::complete::{digit1, line_ending, none_of},
combinator::{map, map_res},
multi::{many1, separated_list1},
IResult,
};
use std::fs;
fn main() -> Result<(), Box<dyn std::error::Error>> {
let input = fs::read_to_string("inputs/day_3.txt")?;
let parsed = PartInventory::parser(&input).unwrap().1;
dbg!(&parsed.part_number_sum());
dbg!(&parsed.gear_ratio_sum());
Ok(())
}
#[derive(Debug)]
struct PartInventory {
parts: Vec<Part>,
symbols: Vec<Symbol>,
}
#[derive(Debug)]
struct Part {
number: u32,
symbols: Vec<char>,
y: usize,
min_x: usize,
max_x: usize,
}
#[derive(Debug, Clone)]
struct Symbol {
symbol: char,
parts: Vec<u32>,
x: usize,
y: usize,
}
#[derive(Debug)]
enum LexToken {
Space(usize),
Part(usize, u32),
Symbol(char),
}
impl PartInventory {
fn parser(input: &str) -> IResult<&str, Self> {
map(LexToken::parser, |tokens| {
let mut parts = Vec::new();
let mut symbols = Vec::new();
for (y, row) in tokens.iter().enumerate() {
let mut x = 0;
for token in row {
match token {
LexToken::Space(_) => {}
LexToken::Part(len, number) => parts.push(Part {
number: *number,
symbols: Vec::new(),
y,
min_x: x,
max_x: x + len - 1,
}),
LexToken::Symbol(symbol) => symbols.push(Symbol {
symbol: *symbol,
parts: Vec::new(),
y,
x,
}),
}
x += token.len();
}
}
for part in &mut parts {
part.symbols = symbols
.iter()
.filter(|symbol| part.touches(symbol))
.map(|symbol| symbol.symbol)
.collect();
}
for symbol in &mut symbols {
symbol.parts = parts
.iter()
.filter(|part| part.touches(symbol))
.map(|part| part.number)
.collect();
}
PartInventory { parts, symbols }
})(input)
}
fn part_number_sum(&self) -> u32 {
self.parts
.iter()
.filter(|part| part.symbols.len() > 0)
.map(|part| part.number)
.sum()
}
fn gear_ratio_sum(&self) -> u32 {
self.symbols
.iter()
.filter(|symbol| symbol.symbol == '*' && symbol.parts.len() == 2)
.map(|symbol| symbol.parts[0] * symbol.parts[1])
.sum()
}
}
impl LexToken {
fn parser(input: &str) -> IResult<&str, Vec<Vec<Self>>> {
separated_list1(
line_ending,
many1(alt((
map(many1(tag(".")), |dots| LexToken::Space(dots.len())),
map_res(digit1, |num_s: &str| {
num_s
.parse()
.map(|num_i| LexToken::Part(num_s.len(), num_i))
}),
map(none_of("\n"), |s| LexToken::Symbol(s)),
))),
)(input)
}
fn len(&self) -> usize {
match self {
Self::Space(len) => *len,
Self::Part(len, _) => *len,
Self::Symbol(_) => 1,
}
}
}
impl Part {
fn touches(&self, symbol: &Symbol) -> bool {
let part = self;
symbol.x >= part.min_x.saturating_sub(1)
&& symbol.x <= part.max_x.saturating_add(1)
&& symbol.y >= part.y.saturating_sub(1)
&& symbol.y <= part.y.saturating_add(1)
}
}
|
