Add solution to 2025-12-11

Author: fuglede

2025/day11/solutions.py

@@ -0,0 +1,27 @@
+from functools import cache
+import networkx as nx
+
+with open("input") as f:
+    ls = f.read().splitlines()
+
+G = nx.DiGraph()
+for l in ls:
+    start, *to = l.split()
+    for p in to:
+        G.add_edge(start[:-1], p)
+
+# Part 1
+print(len(list(nx.all_simple_paths(G, source="you", target="out"))))
+
+
+# Part 2
+@cache
+def paths_from(node, dac_seen, fft_seen):
+    if node == "out":
+        return dac_seen and fft_seen
+    dac_seen = dac_seen or node == "dac"
+    fft_seen = fft_seen or node == "fft"
+    return sum(paths_from(to_node, dac_seen, fft_seen) for to_node in G.neighbors(node))
+
+
+print(paths_from("svr", False, False))