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d12p2.py
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d12p2.py
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from collections import defaultdict
START_NODE = 'start'
END_NODE = 'end'
def count_paths(node, graph, small, visited, small_visited_twice, path):
# keep track of path for fun
if node == END_NODE:
path.append(END_NODE)
print(",".join(path))
path.pop()
return 1
if node in small:
visited.add(node)
path.append(node)
count = 0
for nxt in graph.get(node, []):
if nxt in visited:
if nxt != START_NODE and small_visited_twice is None:
count += count_paths(nxt, graph, small, visited, nxt, path)
continue
count += count_paths(nxt, graph, small, visited, small_visited_twice, path)
if node != small_visited_twice:
visited.discard(node)
path.pop()
return count
if __name__ == '__main__':
graph = defaultdict(list)
small = set()
with open('d12_input.txt', 'r') as f:
for row in f:
s, t = row.strip().split('-')
graph[s].append(t)
graph[t].append(s)
if s == s.lower():
small.add(s)
if t == t.lower():
small.add(t)
print(count_paths(START_NODE, graph, small, set(), None, []))