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const XMAS: &str = "XMAS";
const MAS: &str = "MAS";
type Matrix = Vec<Vec<char>>;
type Position = (usize, usize);
type RowXmas = [Position; XMAS.len()];
type RowMas = [Position; MAS.len()];
fn check_xmas<'a, I>(m: &Matrix, it: I) -> bool
where
I: Iterator<Item = &'a Position>,
{
for (c, (i, j)) in XMAS.chars().zip(it) {
if m[*i][*j] != c {
return false;
}
}
true
}
fn offplus(x: usize, y: isize) -> usize {
(x as isize + y) as usize
}
fn rows_latdiag_from(p: Position, max_x: usize, max_y: usize) -> Vec<RowXmas> {
let mut rs: Vec<RowXmas> = vec![];
// Horizontal / vertical / diagonal
for (p0, (di, dj)) in [
(p, (0, 1)), // horizontal, left-to-right
(p, (1, 0)), // vertical, top-down
(p, (1, 1)), // diag from p, top-down and left-to-right
((p.0, p.1 + XMAS.len() - 1), (1, -1isize)), // the other diag, top-down and right-to-left
] {
// Bounds check
let max_off = XMAS.len();
if p0.0 + di * max_off > max_x
|| (dj > 0 && offplus(p0.1, dj * max_off as isize) > max_y)
|| p0.1 >= max_y
{
continue;
}
let mut p_acc = p0;
let mut ps = [(0, 0); XMAS.len()];
for idx in 0..ps.len() {
ps[idx].0 = p_acc.0;
ps[idx].1 = p_acc.1;
p_acc = (p_acc.0 + di, offplus(p_acc.1, dj));
}
rs.push(ps);
}
rs
}
pub fn p1(input: &str) -> String {
let m: Matrix = input.lines().map(|row| row.chars().collect()).collect();
let mut result = 0;
for i in 0..m.len() {
for j in 0..m[i].len() {
let p = (i, j);
for row in rows_latdiag_from(p, m.len(), m[i].len()) {
if check_xmas(&m, row.iter()) || check_xmas(&m, row.iter().rev()) {
result += 1;
}
}
}
}
result.to_string()
}
fn check_mas<'a, I>(m: &Matrix, it: I) -> bool
where
I: Iterator<Item = &'a Position>,
{
for (c, (i, j)) in MAS.chars().zip(it) {
if m[*i][*j] != c {
return false;
}
}
true
}
fn rows_diag_from(p: Position, max_x: usize, max_y: usize) -> Vec<RowMas> {
let mut rs: Vec<RowMas> = vec![];
// Horizontal / vertical / diagonal
for (p0, (di, dj)) in [
(p, (1, 1)), // diag from p, top-down and left-to-right
((p.0, p.1 + MAS.len() - 1), (1, -1isize)), // the other diag, top-down and right-to-left
] {
// Bounds check
let max_off = MAS.len();
if p0.0 + di * max_off > max_x
|| (dj > 0 && offplus(p0.1, dj * max_off as isize) > max_y)
|| p0.1 >= max_y
{
continue;
}
let mut p_acc = p0;
let mut ps = [(0, 0); MAS.len()];
for idx in 0..ps.len() {
ps[idx].0 = p_acc.0;
ps[idx].1 = p_acc.1;
p_acc = (p_acc.0 + di, offplus(p_acc.1, dj));
}
rs.push(ps);
}
rs
}
pub fn p2(input: &str) -> String {
let m: Matrix = input.lines().map(|row| row.chars().collect()).collect();
let mut result = 0;
for i in 0..=m.len() - MAS.len() {
for j in 0..=m[i].len() - MAS.len() {
let p = (i, j);
let rows = rows_diag_from(p, m.len(), m[i].len());
if rows.iter().all(|r| check_mas(&m, r.iter()) || check_mas(&m, r.iter().rev())) {
result += 1;
}
}
}
result.to_string()
}
|
