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use std::collections::{HashMap, HashSet};
use crate::{Problem, Solution};
pub struct Day03;
impl Problem for Day03 {
const DAY: u8 = 3;
const INPUT: &'static str = include_str!("../input/day_03.txt");
}
impl Solution for Day03 {
type Answer1 = usize;
type Answer2 = usize;
fn part_1(input: &str) -> anyhow::Result<Self::Answer1> {
let grid = input
.trim()
.split('\n')
.map(|l| l.trim().chars().collect::<Vec<_>>())
.collect::<Vec<_>>();
Ok(grid.iter().enumerate().fold(0, |mut acc, (row, line)| {
let line_iter = &mut line.iter().enumerate().peekable();
while line_iter.peek().is_some() {
let (part, is_part) = line_iter
.skip_while(|(_, n)| !n.is_ascii_digit())
.map_while(|(i, n)| n.to_digit(10).map(|u| (i, u)))
.fold((0, false), |(part, is_part), (col, n)| {
let is_part = is_part
|| [row.saturating_sub(1), row, row + 1]
.into_iter()
.flat_map(|r| [col.saturating_sub(1), col, col + 1].map(|c| (r, c)))
.filter(|(r, c)| *r < grid.len() && *c < line.len())
.filter(|(r, c)| *r != row || *c != col)
.flat_map(|(r, c)| grid.get(r).and_then(|line| line.get(c)))
.any(|n| *n != '.' && !n.is_ascii_digit());
(part * 10 + n as usize, is_part)
});
if is_part {
acc += part;
}
}
acc
}))
}
fn part_2(input: &str) -> anyhow::Result<Self::Answer2> {
let grid = input
.trim()
.split('\n')
.map(|l| l.trim().chars().collect::<Vec<_>>())
.collect::<Vec<_>>();
Ok(grid
.iter()
.enumerate()
.fold(
&mut HashMap::<Symbol, HashSet<Part>>::new(),
|acc, (row, line)| {
let line_iter = &mut line.iter().enumerate().peekable();
while line_iter.peek().is_some() {
let (part, symbols) = line_iter
.skip_while(|(_, n)| !n.is_ascii_digit())
.map_while(|(i, n)| n.to_digit(10).map(|u| (i, u)))
.fold(
(Part::default(), HashSet::<Symbol>::new()),
|(mut part, mut neighbors), (col, n)| {
let new_neighbors = [row.saturating_sub(1), row, row + 1]
.into_iter()
.flat_map(|r| {
[col.saturating_sub(1), col, col + 1].map(|c| (r, c))
})
.filter(|(r, c)| *r < grid.len() && *c < line.len())
.filter(|(r, c)| *r != row || *c != col)
.flat_map(|(r, c)| {
grid.get(r)
.and_then(|line| line.get(c))
.map(|n| ((r, c), *n))
})
.filter(|(_, n)| *n != '.' && !n.is_ascii_digit())
.map(Symbol::from);
neighbors.extend(new_neighbors);
part.push_value(n as usize);
(part, neighbors)
},
);
symbols
.into_iter()
.filter(|s| s.value == '*')
.for_each(|s| {
acc.entry(s)
.and_modify(|h| {
h.insert(part);
})
.or_insert(HashSet::from([part]));
});
}
acc
},
)
.values_mut()
.filter(|h| h.len() == 2)
.fold(0, |acc, h| {
acc + h
.iter()
.copied()
.map(|p| p.value)
.reduce(|acc, v| acc * v)
.unwrap()
}))
}
}
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
struct Symbol {
value: char,
pos: (usize, usize),
}
impl From<((usize, usize), char)> for Symbol {
fn from((pos, value): ((usize, usize), char)) -> Self {
Symbol { value, pos }
}
}
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
struct Part {
value: usize,
start: (usize, usize),
end: (usize, usize),
}
impl Part {
fn push_value(&mut self, n: usize) {
self.value = self.value * 10 + n
}
}
#[cfg(test)]
mod tests {
use super::*;
const INPUT: &str = indoc::indoc! {"
467..114..
...*......
..35..633.
......#...
617*......
.....+.58.
..592.....
......755.
...$.*....
.664.598..
"};
#[test]
fn test_part_1() -> anyhow::Result<()> {
Ok(assert_eq!(4361, Day03::part_1(INPUT)?))
}
#[test]
fn test_part_2() -> anyhow::Result<()> {
Ok(assert_eq!(467835, Day03::part_2(INPUT)?))
}
}
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