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use std::str::FromStr;
#[derive(Debug)]
struct Heightmap {
data: Vec<Vec<u8>>,
rows: usize,
cols: usize,
}
impl FromStr for Heightmap {
type Err = ();
fn from_str(s: &str) -> Result<Self, Self::Err> {
let rows: Vec<_> = s.trim().split('\n').collect::<Vec<&str>>();
let mut data: Vec<Vec<u8>> = vec![];
for row in &rows {
data.push(
row.chars()
.map(|x| x.to_digit(10).unwrap() as u8)
.collect::<Vec<u8>>(),
);
}
Ok(Heightmap {
data,
rows: rows.len(),
cols: rows[0].chars().count(),
})
}
}
impl Heightmap {
fn resolve(&self) -> usize {
let mut count: usize = 0;
for i in 0..self.rows {
for j in 0..self.cols {
let top = if i > 0 { self.data[i - 1][j] } else { 10 };
let bottom = if i < self.rows - 1 {
self.data[i + 1][j]
} else {
10
};
let left = if j > 0 { self.data[i][j - 1] } else { 10 };
let right = if j < self.cols - 1 {
self.data[i][j + 1]
} else {
10
};
let center = self.data[i][j];
if center < top && center < bottom && center < left && center < right {
count += (center + 1) as usize;
}
}
}
count
}
}
pub fn part1(input: &str) -> usize {
let grid: Heightmap = input.parse().unwrap();
let result = grid.resolve();
result
}
#[cfg(test)]
mod day9_test {
use super::*;
#[test]
fn test_with_example_data() {
let data = include_str!("../example.txt");
let result = part1(data);
assert_eq!(result, 15);
}
#[test]
fn test_puzzle_input_part1() {
let data = include_str!("../input.txt");
let result = part1(data);
assert_eq!(result, 541);
}
}
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