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#[derive(Debug)]
pub struct Grid<T> {
data: Vec<T>,
width: usize,
height: usize,
}
type Point = (usize, usize);
type Direction = (i64, i64);
pub fn chebyshev_ball(n: i64) -> impl Iterator<Item = Direction> {
(-n..=n).flat_map(move |x| (-n..=n).map(move |y| (x, y)))
}
impl<T> Grid<T> {
pub fn new(grid: Vec<Vec<T>>) -> Grid<T> {
// unfold grid. assume that width/height are consistent
Grid {
height: grid.len(),
width: grid.first().map_or(0, Vec::len),
data: grid.into_iter().flatten().collect(),
}
}
pub fn at(&self, (x, y): Point) -> Option<&T> {
if x >= self.width || y >= self.height {
None
} else {
self.data.get(x + y * self.width)
}
}
pub fn is_in(&self, p: Point) -> bool {
self.at(p).is_some()
}
pub fn points(&self) -> impl Iterator<Item = Point> {
(0..self.width).flat_map(|x| (0..self.height).map(move |y| (x, y)))
}
pub fn move_pos(&self, (x, y): Point, (dx, dy): Direction, n: i64) -> Option<Point> {
let x = (i64::try_from(x).ok()? + n * dx).try_into().ok()?;
let y = (i64::try_from(y).ok()? + n * dy).try_into().ok()?;
let p = (x, y);
if self.is_in(p) { Some(p) } else { None }
}
pub fn ray(&self, p: Point, dp: Direction) -> impl Iterator<Item = &T> {
(0..)
.map(move |n| self.move_pos(p, dp, n))
.take_while(Option::is_some)
.flatten()
.map(|p| self.at(p))
.flatten()
}
}
#[cfg(test)]
mod tests {
use std::collections::HashSet;
use super::*;
#[test]
fn chebyshev_ball_zero() {
assert_eq!(
chebyshev_ball(0).collect::<HashSet<_>>(),
[(0, 0)].iter().cloned().collect()
)
}
#[test]
fn chebyshev_ball_one() {
assert_eq!(
chebyshev_ball(1).collect::<HashSet<_>>(),
[
(-1, -1),
(-1, 0),
(-1, 1),
(0, -1),
(0, 0),
(0, 1),
(1, -1),
(1, 0),
(1, 1)
]
.iter()
.cloned()
.collect()
)
}
#[test]
fn chebyshev_ball_two() {
let points = chebyshev_ball(2).collect::<HashSet<_>>();
assert_eq!(points.len(), 25);
let norms = points
.iter()
.map(|(x, y)| x.abs().max(y.abs()))
.collect::<Vec<_>>();
assert_eq!(norms.iter().filter(|&&n| n == 0).count(), 1);
assert_eq!(norms.iter().filter(|&&n| n == 1).count(), 8);
assert_eq!(norms.iter().filter(|&&n| n == 2).count(), 16);
}
#[test]
fn create_grid() {
let _grid = Grid::new(vec![vec![1, 2, 3], vec![4, 5, 6], vec![7, 8, 9]]);
}
#[test]
fn at_exists() {
let grid = Grid::new(vec![vec![1, 2, 3], vec![4, 5, 6], vec![7, 8, 9]]);
assert_eq!(grid.at((1, 0)).unwrap(), &2);
}
#[test]
fn at_not_exists() {
let grid = Grid::new(vec![vec![1, 2, 3], vec![4, 5, 6], vec![7, 8, 9]]);
assert!(grid.at((17, 10)).is_none());
}
#[test]
fn points_empty() {
let grid = Grid::<u64>::new(vec![vec![]]);
assert!(grid.points().eq(vec![]))
}
#[test]
fn points_equal_size() {
let grid = Grid::new(vec![vec![1, 2], vec![3, 4]]);
let points = grid.points().collect::<HashSet<_>>();
assert_eq!(
points,
[(0, 0), (0, 1), (1, 0), (1, 1)].iter().cloned().collect()
)
}
#[test]
fn points_unequal_size() {
let grid = Grid::new(vec![vec![1, 2], vec![3, 4], vec![5, 6]]);
let points = grid.points().collect::<HashSet<_>>();
assert_eq!(
points,
[(0, 0), (1, 0), (0, 1), (1, 1), (0, 2), (1, 2)]
.iter()
.cloned()
.collect()
)
}
#[test]
fn ray_empty() {
let grid = Grid::<u64>::new(vec![vec![]]);
assert!(grid.ray((1, 1), (1, 2)).eq(vec![].iter()))
}
#[test]
fn ray_single_element() {
let grid = Grid::<u64>::new(vec![vec![1]]);
assert!(grid.ray((0, 0), (1, 2)).eq(vec![1].iter()))
}
#[test]
fn ray_horizontal() {
let grid = Grid::new(vec![vec![1, 2, 3], vec![4, 5, 6], vec![7, 8, 9]]);
assert!(grid.ray((0, 0), (1, 0)).eq(vec![1, 2, 3].iter()))
}
#[test]
fn ray_vertical() {
let grid = Grid::new(vec![vec![1, 2, 3], vec![4, 5, 6], vec![7, 8, 9]]);
assert!(grid.ray((1, 0), (0, 1)).eq(vec![2, 5, 8].iter()))
}
#[test]
fn ray_diagonal() {
let grid = Grid::new(vec![vec![1, 2, 3], vec![4, 5, 6], vec![7, 8, 9]]);
assert!(grid.ray((0, 0), (1, 2)).eq(vec![1, 8].iter()))
}
}
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