garnet/rust/puzzles/day5.rs
George Thomas 70b56f4501 Use new type for day 5 ranges
This is cleaner and faster, with inherent methods and mutability.
2026-01-07 14:29:47 +00:00

90 lines
2.2 KiB
Rust

use crate::puzzle::Puzzle;
use nom::{
Parser,
character::complete::{char, newline, usize},
combinator::eof,
error::Error,
multi::{separated_list0, separated_list1},
sequence::{separated_pair, terminated},
};
pub const PUZZLE: Puzzle<(Vec<Range>, Vec<usize>), 2> = Puzzle {
number: 5,
parser: |input| {
terminated::<_, _, Error<&str>, _, _>(
separated_pair(
separated_list1(
newline,
separated_pair(usize, char('-'), usize)
.map(|(lower, upper)| Range { lower, upper }),
),
(newline, newline),
separated_list0(newline, usize),
),
(newline, eof),
)
.parse(input)
.unwrap()
.1
},
parts: [
|(ranges, vals)| {
vals.iter()
.filter(|v| ranges.iter().any(|r| r.contains(**v)))
.count()
.to_string()
},
|(ranges, _)| {
let mut sorted_ranges = ranges.clone();
sorted_ranges.sort_by_key(|r| r.lower);
let mut merged = Ranges::new();
for r in sorted_ranges {
merged.add(r);
}
merged.total_length().to_string()
},
],
};
#[derive(Clone, Debug)]
pub struct Range {
lower: usize,
upper: usize,
}
impl Range {
fn length(&self) -> usize {
self.upper - self.lower + 1
}
fn contains(&self, n: usize) -> bool {
n >= self.lower && n <= self.upper
}
fn extend(&self, upper: usize) -> Range {
Range {
lower: self.lower,
upper: self.upper.max(upper),
}
}
}
struct Ranges(Vec<Range>);
impl Ranges {
fn new() -> Self {
Ranges(Vec::new())
}
fn add(&mut self, new: Range) {
if self.0.is_empty() {
self.0.push(new);
} else {
let first = &self.0[0];
if first.contains(new.lower) {
self.0[0] = first.extend(new.upper);
} else {
self.0.insert(0, new);
}
}
}
fn total_length(&self) -> usize {
self.0.iter().map(|r| r.length()).sum()
}
}