day 4 pt 1 & 2

some parts stolen from the internet but i learned a lot

src/bin/04.rs

@@ -0,0 +1,68 @@
+advent_of_code::solution!(4);
+use itertools::Itertools;
+use tap::Pipe;
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let grid = input.lines().map(|l| l.chars().collect_vec()).collect_vec();
+    let row_size = grid.len() as isize;
+    let col_size = grid[0].len() as isize;
+    let is_valid = |row_idx, col_idx| (0..row_size).contains(&row_idx) && (0..col_size).contains(&col_idx);
+    let get_value = |row_idx, col_idx| is_valid(row_idx, col_idx).then(|| grid[row_idx as usize][col_idx as usize]);
+
+    let total: i32 = Itertools::cartesian_product(0..row_size, 0..col_size)
+    .flat_map(|(row_idx, col_idx)| {
+        [(0, -1), (-1, 0), (-1, -1), (-1, 1)]
+        .into_iter()
+        .map(move |(row_direction, col_direction)| {
+            (0..=3)
+            .filter_map(
+                |magnitude| get_value(row_idx + row_direction * magnitude, col_idx + col_direction * magnitude)
+            )
+            .collect::<String>()
+            .pipe(|s| ["XMAS", "SAMX"].contains(&s.as_ref()) as i32)
+        })
+    }).sum();
+
+    Some(total as u32)
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    let grid = input.lines().map(|l| l.chars().collect_vec()).collect_vec();
+    let row_size = grid.len() as isize;
+    let col_size = grid[0].len() as isize;
+    let is_valid = |row_idx, col_idx| (0..row_size).contains(&row_idx) && (0..col_size).contains(&col_idx);
+    let get_value = |row_idx, col_idx| is_valid(row_idx, col_idx).then(|| grid[row_idx as usize][col_idx as usize]);
+
+    let total= Itertools::cartesian_product(0..row_size, 0..col_size)
+    .filter_map(|(row_idx, col_idx)| {
+        if get_value(row_idx, col_idx) != Some('A') { return None }
+
+        let first = [(row_idx - 1, col_idx - 1), (row_idx, col_idx), (row_idx+1, col_idx+1)].iter().filter_map(|(row, col)| get_value(*row, *col)).collect::<String>();
+        if !["MAS", "SAM"].contains(&first.as_ref()) { return None }
+
+        let second = [(row_idx - 1, col_idx + 1), (row_idx, col_idx), (row_idx+1, col_idx-1)].iter().filter_map(|(row, col)| get_value(*row, *col)).collect::<String>();
+        if !["MAS", "SAM"].contains(&second.as_ref()) { return None }
+
+        Some(true)
+    }).count();
+
+    Some(total as u32)
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(18));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(9));
+    }
+}