32 lines
837 B
Python
32 lines
837 B
Python
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from fixtures import unweighted_digraph
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from collections import deque
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# vertices_no_in_edges :: UnweightedDigraph -> Set(Vertex)
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def vertices_no_in_edges(g):
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"""Return the vertices in graph `g` with no in-edges."""
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result = set()
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vertices = set(g.keys())
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for neighbors in g.values():
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result = result.union(neighbors)
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return vertices ^ result
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# topo_sort :: UnweightedDigraph -> List(Vertex)
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def topo_sort(g):
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q = deque()
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seen = set()
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result = []
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for x in vertices_no_in_edges(g):
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q.append(x)
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while q:
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vertex = q.popleft()
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if vertex in seen:
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continue
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result.append(vertex)
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neighbors = g.get(vertex)
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for x in g.get(vertex):
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q.append(x)
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seen.add(vertex)
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return result
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print(topo_sort(unweighted_digraph))
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