Solve 2025 day 11 pt 1-2

For p1 a BFS algorithm is fast enough. For pt 2,
for the third day in a row, it did not work.

I caved in and used recursion and memoisation for
DFS instead, instantly fast as lightning.

I finished by making the pt 2 code compatible with
pt 1.

2025-python/output/day_11.py

@@ -0,0 +1,33 @@
+import functools
+from collections import defaultdict
+
+
+def solve(data):
+    G = defaultdict(set)
+    for line in data.splitlines():
+        f, *t = line.split()
+        G[f[:-1]] = set(t)
+
+    @functools.cache
+    def _traverse(k, fasttrack=True, fft=False, dac=False):
+        if k == "out":
+            return fasttrack or (fft and dac)
+        return sum(
+            _traverse(nk, fasttrack, fft or k == "fft", dac or k == "dac")
+            for nk in G[k]
+        )
+
+    return _traverse("you"), _traverse("svr", fasttrack=False)
+
+
+if __name__ == "__main__":
+    with open("./input/11.txt", "r") as f:
+        inp = f.read().strip()
+
+    p1, p2 = solve(inp)
+
+    print(p1)
+    print(p2)
+
+    assert p1 == 649
+    assert p2 == 458948453421420