Update day 12 solution

Only count the number of sub-paths for part 2

day-12/day-12.py

@@ -23,13 +23,12 @@ def process_node(node, available_edges, visited):
 
 
 def process_node_twice(node, available_edges, visited, visited_twice):
-    paths = deque()
+    num_paths = 0
     if node == "end":
-        paths.append(deque(node))
-        return paths
+        return 1
     if node.islower():
         if node in visited and visited_twice:
-            return paths
+            return num_paths
         elif node in visited and node != "start":
             visited_twice = node
         else:
@@ -37,15 +36,12 @@ def process_node_twice(node, available_edges, visited, visited_twice):
     neighbors = [n for e in available_edges if node in e for n in e if n != node]
     for n in neighbors:
         if n not in visited or visited_twice != node and n != "start":
-            nxt = process_node_twice(n, available_edges, visited, visited_twice)
-            for p in nxt:
-                p.appendleft(node)
-            paths += nxt
+            num_paths += process_node_twice(n, available_edges, visited, visited_twice)
     if visited_twice == node:
         visited_twice = None
     elif node in visited:
         visited.remove(node)
-    return paths
+    return num_paths
 
 
 def part_1(input):
@@ -67,8 +63,7 @@ def part_2(input):
         n_start, n_end = line.strip().split('-')
         e = (n_start, n_end)
         edges.append(e)
-    paths = process_node_twice("start", edges, set(), None)
-    result = len(paths)
+    result = process_node_twice("start", edges, set(), None)
     print("Part 2 result:", result)