1 files changed, 21 insertions, 1 deletions
diff --git a/src/bin/day4.rs b/src/bin/day4.rs
index 9a256a7..768ca25 100644
--- a/src/bin/day4.rs
+++ b/src/bin/day4.rs
@@ -5,7 +5,7 @@ static DAY: u8 = 4;
 fn main() {
     let input = advent::read_lines(DAY);
     println!("{DAY}a: {}", count_xmas(&input));
-    println!("{DAY}b: {}", 0);
+    println!("{DAY}b: {}", count_x_mas(&input));
 }
 
 fn get_letter_grid(input: &[String]) -> HashMap<(isize,isize), char> {
@@ -86,6 +86,25 @@ fn count_xmas(input: &[String]) -> usize {
     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::*;
@@ -105,5 +124,6 @@ mod tests {
             "MXMXAXMASX",
         ].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
         assert_eq!(count_xmas(&input), 18);
+        assert_eq!(count_x_mas(&input), 9);
     }
 }