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33 lines
1.3 KiB
Python
33 lines
1.3 KiB
Python
# Generate all possible single-root message thread structures of size
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# argv[1]. Each output line is a thread structure, where the n'th
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# field is either a number giving the parent of message n or "None"
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# for the root.
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import sys
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from itertools import chain, combinations
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def subsets(s):
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return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))
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nodes = set(range(int(sys.argv[1])))
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# Queue of (tree, free, to_expand) where tree is a {node: parent}
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# dictionary, free is a set of unattached nodes, and to_expand is
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# itself a queue of nodes in the tree that need to be expanded.
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# The queue starts with all single-node trees.
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queue = [({root: None}, nodes - {root}, (root,)) for root in nodes]
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# Process queue
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while queue:
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tree, free, to_expand = queue.pop()
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if len(to_expand) == 0:
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# Only print full-sized trees
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if len(free) == 0:
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print(" ".join(map(str, [msg[1] for msg in sorted(tree.items())])))
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else:
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# Expand node to_expand[0] with each possible set of children
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for children in subsets(free):
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ntree = {child: to_expand[0] for child in children}
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ntree.update(tree)
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nfree = free.difference(children)
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queue.append((ntree, nfree, to_expand[1:] + tuple(children)))
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