Day 25

.gitignore

@@ -1 +1,2 @@
 AoC2021/Bene/
+__pycache__

2021/Bene/main.py

@@ -0,0 +1,28 @@
+#!/bin/env python3
+import sys
+import string
+from collections import Counter
+
+def isSmall(node): return all(c in string.ascii_lowercase for c in node)
+
+def ext(path, ns, visits=1):
+    if path[-1] == 'end': return (yield path)
+    for n in ns[path[-1]]:
+        if n == 'start': continue
+        ext = path + (n,)
+        m = list(map(lambda x: x[1], Counter(n for n in ext if isSmall(n)).most_common(2)))
+        if m[0] > visits or len(m) > 1 and m[1] > 1: continue
+        yield ext
+
+if __name__ == '__main__':
+    edges = [line.strip().split('-') for line in open(sys.argv[1])]
+    ns = { n: set() for e in edges for n in e }
+    for a,b in edges: ns[a].add(b); ns[b].add(a)
+    
+    ps = set([('start',)])
+    while (n := set(np for p in ps for np in ext(p, ns))) != ps: ps = n
+    print(len(ps))
+
+    ps = set([('start',)])
+    while (n := set(np for p in ps for np in ext(p, ns, visits=2))) != ps: ps = n
+    print(len(ps))