day 4 puzzle 2

src/day4/puzzle2.typ

@@ -0,0 +1,33 @@
+#import "/src/utils.typ": *
+
+#let solve(input) = {
+  let lines = input.split("\n")
+  let w = lines.first().len()
+  let h = lines.len()
+
+  let perms = (("M", "S"), ("S", "M"))
+  let total = 0
+  for y in range(1, h - 1) {
+    for x in range(1, w - 1) {
+      if lines.at(y).at(x) == "A" {
+        let tl = lines.at(y - 1).at(x - 1)
+        let tr = lines.at(y - 1).at(x + 1)
+        let bl = lines.at(y + 1).at(x - 1)
+        let br = lines.at(y + 1).at(x + 1)
+        let tlbr = (tl, br)
+        let bltr = (bl, tr)
+        if tlbr in perms and bltr in perms {
+          total += 1
+        }
+      }
+    }
+  }
+
+  return total
+}
+
+#show-puzzle(
+  4, 2,
+  solve,
+  example: 9
+)