Solve Day 4 Part 1

data/examples/04.txt

@@ -0,0 +1,10 @@
+MMMSXXMASM
+MSAMXMSMSA
+AMXSXMAAMM
+MSAMASMSMX
+XMASAMXAMM
+XXAMMXXAMA
+SMSMSASXSS
+SAXAMASAAA
+MAMMMXMMMM
+MXMXAXMASX

src/bin/04.rs

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+advent_of_code::solution!(4);
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let matrix: Vec<Vec<char>> = input.lines().map(|line| line.chars().collect()).collect();
+    let m = matrix.len() as i32;
+    let n = matrix[0].len() as i32;
+
+    let check_pos = |row: i32, col: i32| -> i32 {
+        let xmas = "XMAS";
+        let dirs = [
+            (0, 1),
+            (0, -1),
+            (-1, 0),
+            (1, 0),
+            (-1, -1),
+            (-1, 1),
+            (1, -1),
+            (1, 1),
+        ];
+
+        let mut result = 0;
+
+        'outer: for (dr, dc) in dirs {
+            for i in 0..4 {
+                let (r, c) = (row + (i * dr), col + (i * dc));
+                if r >= 0 && c >= 0 && r < m && c < n {
+                    if xmas.chars().nth(i as usize).unwrap()
+                        != matrix[r as usize][c as usize]
+                    {
+                        continue 'outer;
+                    }
+                } else {
+                    continue 'outer;
+                }
+            }
+            result += 1;
+        }
+
+        return result;
+    };
+
+    let mut count = 0;
+
+    for i in 0..m {
+        for j in 0..n {
+            count += check_pos(i, j);
+        }
+    }
+
+    Some(count as u32)
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    None
+}
+
+#[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, None);
+    }
+}