From efb1e3e55176554dda2f6947f2173dac738a3aa9 Mon Sep 17 00:00:00 2001
From: felixm <mail@felixm.de>
Date: Thu, 12 Dec 2024 23:57:04 -0500
Subject: [PATCH] Solve 2024 day 12

---
 2024/d12.py | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 README.md   |  5 +++--
 2 files changed, 64 insertions(+), 2 deletions(-)
 create mode 100644 2024/d12.py

diff --git a/2024/d12.py b/2024/d12.py
new file mode 100644
index 0000000..0f57ff7
--- /dev/null
+++ b/2024/d12.py
@@ -0,0 +1,61 @@
+from lib import get_data
+from lib import Grid2D
+from collections import defaultdict
+from collections import deque
+
+data = get_data(__file__)
+
+DIRS = {
+    "N": (-1, 0),
+    "E": (0, 1),
+    "S": (1, 0),
+    "W": (0, -1),
+}.values()
+
+
+g = Grid2D(data)
+cs = defaultdict(set)
+for row in range(g.n_rows):
+    for col in range(g.n_cols):
+        c = g[(row, col)]
+        cs[c].add((row, col))
+
+t1, t2 = 0, 0
+for c, cs in cs.items():
+    while cs:
+        peri = 0
+        start = cs.pop()
+        seen = set()
+        queue = deque([start])
+        fences = set()
+        while queue:
+            pos = queue.popleft()
+            if pos in seen:
+                continue
+            seen.add(pos)
+
+            for d in DIRS:
+                nb = d[0] + pos[0], d[1] + pos[1]
+                if g.contains(nb) and g[nb] == c:
+                    queue.append(nb)
+                    cs.discard(nb)
+                else:
+                    peri += 1
+                    nb = tuple(list(nb) + [d])
+                    fences.add(nb)
+
+        nfences = set()
+        for row, col, dir in fences:
+            for dr, dc in [(1, 0), (0, 1)]:
+                nr, nc = row + dr, col + dc
+                if (nr, nc, dir) in fences:
+                    break
+            else:
+                nfences.add((row, col, dir))
+
+        c_area = len(seen)
+        t1 += c_area * peri
+        t2 += c_area * len(nfences)
+
+print(t1)
+print(t2)
diff --git a/README.md b/README.md
index b148962..536e504 100644
--- a/README.md
+++ b/README.md
@@ -301,6 +301,7 @@ and focus. Of course, learning more algorithms and techniques helps.
 - Day  8: `00:15:59  1742      0   00:26:56  2190      0`
 - Day  9: `00:48:23  6055      0   01:09:38  3159      0`
 - Day 10: `00:19:47  2976      0   00:20:47  2244      0`
-- Day 11: `11   00:05:13   642      0   00:33:07  2673      0`
-
+- Day 11: `00:05:13   642      0   00:33:07  2673      0`
+- Day 12: `00:30:30  3540      0   11:41:33  16212     0`
+- Day 13: