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|
use std::collections::HashMap;
static DAY: u8 = 4;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", count_xmas(&input));
println!("{DAY}b: {}", count_x_mas(&input));
}
fn get_letter_grid(input: &[String]) -> HashMap<(isize,isize), char> {
let mut grid = HashMap::new();
for (y, line) in input.iter().enumerate() {
for (x, c) in line.chars().enumerate() {
grid.insert((x as isize, y as isize), c);
}
}
grid
}
fn word_search(grid: &HashMap<(isize,isize), char>, x: isize, y: isize, diffx: isize, diffy: isize, word: &str) -> bool {
for (i, c) in word.chars().enumerate() {
let i = i as isize;
if let Some(letter) = grid.get(&(x + i*diffx, y + i*diffy)) {
if *letter != c {
return false;
}
} else {
return false;
}
}
true
}
fn word_up(grid: &HashMap<(isize,isize), char>, x: isize, y: isize, word: &str) -> bool {
word_search(grid, x, y, 0, -1, word)
}
fn word_down(grid: &HashMap<(isize,isize), char>, x: isize, y: isize, word: &str) -> bool {
word_search(grid, x, y, 0, 1, word)
}
fn word_left(grid: &HashMap<(isize,isize), char>, x: isize, y: isize, word: &str) -> bool {
word_search(grid, x, y, -1, 0, word)
}
fn word_right(grid: &HashMap<(isize,isize), char>, x: isize, y: isize, word: &str) -> bool {
word_search(grid, x, y, 1, 0, word)
}
fn word_ne(grid: &HashMap<(isize,isize), char>, x: isize, y: isize, word: &str) -> bool {
word_search(grid, x, y, 1, -1, word)
}
fn word_se(grid: &HashMap<(isize,isize), char>, x: isize, y: isize, word: &str) -> bool {
word_search(grid, x, y, 1, 1, word)
}
fn word_sw(grid: &HashMap<(isize,isize), char>, x: isize, y: isize, word: &str) -> bool {
word_search(grid, x, y, -1, 1, word)
}
fn word_nw(grid: &HashMap<(isize,isize), char>, x: isize, y: isize, word: &str) -> bool {
word_search(grid, x, y, -1, -1, word)
}
fn count_xmas(input: &[String]) -> usize {
let grid = get_letter_grid(input);
let max_y = input.len() as isize;
let max_x = input[0].len() as isize;
let mut xmas_count = 0;
for x in 0..max_x {
for y in 0..max_y {
if word_up(&grid, x, y, "XMAS") { xmas_count += 1; }
if word_down(&grid, x, y, "XMAS") { xmas_count += 1; }
if word_left(&grid, x, y, "XMAS") { xmas_count += 1; }
if word_right(&grid, x, y, "XMAS") { xmas_count += 1; }
if word_ne(&grid, x, y, "XMAS") { xmas_count += 1; }
if word_se(&grid, x, y, "XMAS") { xmas_count += 1; }
if word_sw(&grid, x, y, "XMAS") { xmas_count += 1; }
if word_nw(&grid, x, y, "XMAS") { xmas_count += 1; }
}
}
xmas_count
}
fn count_x_mas(input: &[String]) -> usize {
let grid = get_letter_grid(input);
let max_y = input.len() as isize;
let max_x = input[0].len() as isize;
let mut xmas_count = 0;
for x in 0..max_x {
for y in 0..max_y {
for word1 in ["MAS", "SAM"] {
for word2 in ["MAS", "SAM"] {
if word_se(&grid, x, y, word1) && word_sw(&grid, x+2, y, word2) { xmas_count += 1; }
}
}
}
}
xmas_count
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = [
"MMMSXXMASM",
"MSAMXMSMSA",
"AMXSXMAAMM",
"MSAMASMSMX",
"XMASAMXAMM",
"XXAMMXXAMA",
"SMSMSASXSS",
"SAXAMASAAA",
"MAMMMXMMMM",
"MXMXAXMASX",
].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
assert_eq!(count_xmas(&input), 18);
assert_eq!(count_x_mas(&input), 9);
}
}
|
