Day4

day4/rust/src/main.rs

@@ -0,0 +1,111 @@
+struct Direction {
+    x: isize,
+    y: isize,
+}
+
+struct Map {
+    map: Vec<Vec<char>>,
+    rows: usize,
+    columns: usize,
+}
+
+impl Map {
+    fn get(&self, x: isize, y: isize) -> Option<char> {
+        if x < 0 || y < 0 || x > (self.rows as isize) - 1 || y > (self.columns as isize) - 1 {
+            return None;
+        }
+
+        Some(self.map[x as usize][y as usize])
+    }
+}
+
+fn main() {
+    let stdin = std::io::stdin();
+    let mut map = Vec::new();
+
+    for line in stdin.lines() {
+        let line = line.unwrap();
+
+        let levels: Vec<_> = line.chars().collect();
+
+        map.push(levels);
+    }
+
+    let rows = map.len();
+    let columns = map[0].len();
+
+    let map = Map { map, rows, columns };
+
+    let search_sequence: Vec<_> = "XMAS".chars().collect();
+
+    let directions = vec![
+        Direction { x: 0, y: 1 },
+        Direction { x: 0, y: -1 },
+        Direction { x: 1, y: 0 },
+        Direction { x: -1, y: 0 },
+        Direction { x: 1, y: 1 },
+        Direction { x: 1, y: -1 },
+        Direction { x: -1, y: 1 },
+        Direction { x: -1, y: -1 },
+    ];
+
+    let mut count = 0;
+    let mut count2 = 0;
+
+    for x in 0..map.rows {
+        for y in 0..map.columns {
+            for dir in &directions {
+                let mut found = true;
+                for (idx, &s) in search_sequence.iter().enumerate() {
+                    let row = x as isize + idx as isize * dir.x;
+                    let column = y as isize + idx as isize * dir.y;
+                    match map.get(row, column) {
+                        None => {
+                            found = false;
+                            break;
+                        }
+                        Some(value) => {
+                            if value != s {
+                                found = false;
+                                break;
+                            }
+                        }
+                    }
+                }
+
+                if found {
+                    count += 1;
+                }
+            }
+
+            // Part 2
+            if let Some('A') = map.get(x as isize, y as isize) {
+                let row = x as isize;
+                let column = y as isize;
+                match (
+                    map.get(row - 1, column - 1),
+                    map.get(row + 1, column + 1),
+                    map.get(row + 1, column - 1),
+                    map.get(row - 1, column + 1),
+                ) {
+                    (Some('M'), Some('S'), Some('M'), Some('S')) => {
+                        count2 += 1;
+                    }
+                    (Some('S'), Some('M'), Some('M'), Some('S')) => {
+                        count2 += 1;
+                    }
+                    (Some('M'), Some('S'), Some('S'), Some('M')) => {
+                        count2 += 1;
+                    }
+                    (Some('S'), Some('M'), Some('S'), Some('M')) => {
+                        count2 += 1;
+                    }
+                    _ => (),
+                }
+            }
+        }
+    }
+
+    println!("{}", count);
+    println!("{}", count2);
+}