day 12 puzzle 1

progress.yaml

@@ -20,3 +20,5 @@
   stars: 2
 11:
   stars: 2
+12:
+  stars: 1

res/examples/day12_1.txt

@@ -0,0 +1,4 @@
+AAAA
+BBCD
+BBCC
+EEEC

res/examples/day12_2.txt

@@ -0,0 +1,5 @@
+OOOOO
+OXOXO
+OOOOO
+OXOXO
+OOOOO

res/examples/day12_3.txt

@@ -0,0 +1,10 @@
+RRRRIICCFF
+RRRRIICCCF
+VVRRRCCFFF
+VVRCCCJFFF
+VVVVCJJCFE
+VVIVCCJJEE
+VVIIICJJEE
+MIIIIIJJEE
+MIIISIJEEE
+MMMISSJEEE

src/day12/puzzle1.typ

@@ -0,0 +1,68 @@
+#import "/src/utils.typ": *
+
+#let offsets = (
+  (-1, 0),
+  (0, -1),
+  (1, 0),
+  (0, 1)
+)
+
+#let in-grid(w, h, x, y) = {
+  return 0 <= x and x < w and 0 <= y and y < h
+}
+
+#let solve(input) = {
+  let grid = input.split("\n").map(l => l.clusters())
+  let w = grid.first().len()
+  let h = grid.len()
+  let in-grid = in-grid.with(w, h)
+
+  let visited = ((false,) * w,) * h
+  let total = 0
+
+  for y in range(h) {
+    for x in range(w) {
+      if visited.at(y).at(x) {
+        continue
+      }
+      let char = grid.at(y).at(x)
+      let cells = ()
+      let borders = 0
+      let next-cells = ((x, y),)
+      while next-cells.len() != 0 {
+        let (cx, cy) = next-cells.remove(0)
+        cells.push((cx, cy))
+        visited.at(cy).at(cx) = true
+        for (dx, dy) in offsets {
+          let (x2, y2) = (cx + dx, cy + dy)
+          if (x2, y2) in cells or (x2, y2) in next-cells {
+            continue
+          }
+          if in-grid(x2, y2) {
+            let char2 = grid.at(y2).at(x2)
+            if char2 == char {
+              next-cells.push((x2, y2))
+            } else {
+              borders += 1
+            }
+          } else {
+            borders += 1
+          }
+        }
+      }
+      total += borders * cells.len()
+    }
+  }
+
+  return total
+}
+
+#show-puzzle(
+  12, 1,
+  solve,
+  example: (
+    "1": 140,
+    "2": 772,
+    "3": 1930
+  )
+)