49 lines
1.3 KiB
Python
49 lines
1.3 KiB
Python
import re
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input_pattern = re.compile(r'([a-zA-Z]+)-([a-zA-Z]+)')
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small_pattern = re.compile(r'([a-z]+)')
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def load():
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with open('../.input/day12', 'r') as f:
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return input_pattern.findall(f.read())
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def construct_paths(graph, start, end, path=None, single_reentry=False):
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if path is None:
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path = [start]
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if start == end:
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yield path
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else:
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for node in graph[start]:
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is_small = small_pattern.match(node)
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if not is_small or node not in path:
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yield from construct_paths(graph, node, end, path + [node], single_reentry)
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elif is_small and single_reentry and node not in ["start", "end"]:
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yield from construct_paths(graph, node, end, path + [node])
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def solve1():
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graph = {}
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for node1, node2 in load():
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graph.setdefault(node1, set()).add(node2)
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graph.setdefault(node2, set()).add(node1)
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return sum(1 for _ in construct_paths(graph, 'start', 'end'))
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def solve2():
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graph = {}
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for node1, node2 in load():
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graph.setdefault(node1, set()).add(node2)
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graph.setdefault(node2, set()).add(node1)
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return sum(1 for _ in construct_paths(graph, 'start', 'end', single_reentry=True))
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if __name__ == '__main__':
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print(solve1()) # 4304
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print(solve2()) # 118242
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