added visualization for day 4 puzzle 1

src/day4/puzzle1.typ

@@ -1,10 +1,11 @@
 #import "/src/utils.typ": *
+#import "@preview/cetz:0.3.1": canvas, draw
 
 #let check-xmas(lines, ox, oy) = {
   let w = lines.first().len()
   let h = lines.len()
 
-  let total = 0
+  let dirs = ()
   for dy in (-1, 0, 1) {
     for dx in (-1, 0, 1) {
       if dx == 0 and dy == 0 {
@@ -26,11 +27,11 @@
         }
       }
       if buffer == "XMAS" {
-        total += 1
+        dirs.push((dx, dy))
       }
     }
   }
-  return total
+  return dirs
 }
 
 #let solve(input) = {
@@ -42,7 +43,7 @@
   for y in range(h) {
     for x in range(w) {
       if lines.at(y).at(x) == "X" {
-        total += check-xmas(lines, x, y)
+        total += check-xmas(lines, x, y).len()
       }
     }
   }
@@ -50,8 +51,41 @@
   return total
 }
 
+#let visualize(input) = {
+  let lines = input.split("\n")
+  let w = lines.first().len()
+  let h = lines.len()
+
+  canvas({
+    for y in range(h) {
+      for x in range(w) {
+        if lines.at(y).at(x) == "X" {
+          let key = str(x) + "-" + str(y)
+          let dirs = check-xmas(lines, x, y)
+          draw.on-layer(2, {
+            for (dx, dy) in dirs {
+              draw.line(
+                (x + dx * 0.2, y + dy * 0.2),
+                (x + dx * 2.8, y + dy * 2.8),
+                stroke: red,
+                fill: red,
+                mark: (end: ">")
+              )
+            }
+          })
+        }
+        draw.content(
+          (x, y),
+          lines.at(y).at(x)
+        )
+      }
+    }
+  })
+}
+
 #show-puzzle(
   4, 1,
   solve,
-  example: 18
+  example: 18,
+  visualize: visualize
 )