Solve 2024 day 6

2024/d6.py

@@ -0,0 +1,55 @@
+from lib import get_data
+from lib import Grid2D
+
+data = get_data(__file__)
+
+
+DIRS = {
+    "N": (-1, 0),
+    "E": (0, 1),
+    "S": (1, 0),
+    "W": (0, -1),
+}
+DIRSL = "NESW"
+
+g = Grid2D(data)
+
+t = 0
+for rr in range(g.n_rows):
+    for cc in range(g.n_cols):
+        (p,) = g.find("^")
+
+        seen = set()
+        dirl = "N"
+        dir = DIRS["N"]
+
+        loop = False
+
+        if g[(rr, cc)] == "#" or g[(rr, cc)] == "^":
+            continue
+
+        g[(rr, cc)] = "#"
+
+        while True:
+            if (p, dir) in seen:
+                loop = True
+                break
+            seen.add((p, dir))
+            r, c = p[0] + dir[0], p[1] + dir[1]
+            if not (0 <= r < g.n_rows and 0 <= c < g.n_cols):
+                break
+
+            if g[(r, c)] == "#":
+                dirl = DIRSL[(DIRSL.index(dirl) + 1) % 4]
+                dir = DIRS[dirl]
+
+            else:
+                p = (r, c)
+
+        g[(rr, cc)] = "."
+
+        if loop:
+            t += 1
+
+print(len(set(pos for pos, _ in seen)))
+print(t)

README.md

@@ -296,3 +296,5 @@ and focus. Of course, learning more algorithms and techniques helps.
 - Day 3: `00:01:48   165      0   00:02:40    56     45`
 - Day 4: `00:07:47  1101      0   00:24:07  2410      0`
 - Day 5: `00:07:07   679      0   00:23:02  1998      0`
+- Day 6: `00:09:43  1082      0   00:16:29   464      0`
+