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use aoc2024::matrix;
use std::collections::HashSet;
static AROUND_DELTAS: [(isize, isize); 4] = [(-1, 0), (0, -1), (0, 1), (1, 0)];
type Matrix = matrix::Matrix<u32>;
type Trailhead = matrix::Pos;
fn trailheads(m: &Matrix) -> Vec<Trailhead> {
let mut result: Vec<Trailhead> = vec![];
for i in 0..m.limit.0 {
for j in 0..m.limit.1 {
let pos = (i, j);
if m.get(pos) == &0 {
result.push(pos);
}
}
}
result
}
fn reachable(m: &Matrix, pos: matrix::Pos) -> HashSet<matrix::Pos> {
let height = m.get(pos);
AROUND_DELTAS
.iter()
.filter_map(|&d| m.pos_move(pos, d))
.filter(|&p| *m.get(p) == height + 1)
.collect()
}
fn score1(m: &Matrix, th: Trailhead) -> u32 {
let mut heads: HashSet<matrix::Pos> = HashSet::new();
heads.insert(th);
let mut height = 0;
while height < 9 {
heads = heads.into_iter().flat_map(|th| reachable(m, th)).collect();
height += 1;
}
heads.len() as u32
}
fn p1(input: &str) -> String {
let m: Matrix = matrix::Matrix::new(input, |c| c.to_digit(10).unwrap());
let result: u32 = trailheads(&m).iter().map(|&th| score1(&m, th)).sum();
result.to_string()
}
fn score2(m: &Matrix, th: Trailhead) -> u32 {
let mut heads: Vec<matrix::Pos> = vec![th];
let mut height = 0;
while height < 9 {
heads = heads.into_iter().flat_map(|th| reachable(m, th)).collect();
height += 1;
}
heads.len() as u32
}
fn p2(input: &str) -> String {
let m: Matrix = matrix::Matrix::new(input, |c| c.to_digit(10).unwrap());
let result: u32 = trailheads(&m).iter().map(|&th| score2(&m, th)).sum();
result.to_string()
}
fn main() {
aoc2024::run_day("10", p1, p2);
}
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