Solve 2021 day 20, 21, 23, 25

2021/d25.py

@@ -0,0 +1,29 @@
+from lib import get_data
+from lib import Grid2D
+
+data = get_data(__file__)
+
+g = Grid2D(data)
+seen = set()
+for i in range(10**9):
+    if g.hash() in seen:
+        print(i)
+        break
+
+    seen.add(g.hash())
+    blocked = set(g.find(">v"))
+    for p in g.find(">"):
+        np = (p[0], (p[1] + 1) % g.n_cols)
+        if np in blocked:
+            continue
+        g[p] = "."
+        g[np] = ">"
+
+    blocked = set(g.find(">v"))
+    for p in g.find("v"):
+        np = ((p[0] + 1) % g.n_rows , p[1])
+        if np in blocked:
+            continue
+        g[p] = "."
+        g[np] = "v"
+