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42 lines
1.1 KiB
Python
42 lines
1.1 KiB
Python
"""Topological Sort."""
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# a
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# / \
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# b c
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# / \
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# d e
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edges: dict[str, list[str]] = {
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"a": ["c", "b"],
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"b": ["d", "e"],
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"c": [],
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"d": [],
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"e": [],
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}
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vertices: list[str] = ["a", "b", "c", "d", "e"]
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def topological_sort(start: str, visited: list[str], sort: list[str]) -> list[str]:
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"""Perform topological sort on a directed acyclic graph."""
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current = start
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# add current to visited
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visited.append(current)
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neighbors = edges[current]
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for neighbor in neighbors:
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# if neighbor not in visited, visit
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if neighbor not in visited:
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sort = topological_sort(neighbor, visited, sort)
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# if all neighbors visited add current to sort
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sort.append(current)
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# if all vertices haven't been visited select a new one to visit
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if len(visited) != len(vertices):
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for vertice in vertices:
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if vertice not in visited:
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sort = topological_sort(vertice, visited, sort)
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# return sort
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return sort
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if __name__ == "__main__":
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sort = topological_sort("a", [], [])
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print(sort)
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