48 lines
1.2 KiB
Python
48 lines
1.2 KiB
Python
from collections import deque
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# This is a solution which uses DFS to trace the paths; there
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# are other solutions as well
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classes = {
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'CPSC 230': {'CPSC 231'},
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'CPSC 231': {'CPSC 350', 'CPSC 330'},
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'CPSC 350': {'CPSC 380', 'CPSC 408', 'CPSC 406'},
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'CPSC 330': {'CPSC 351'},
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'CPSC 351': set(),
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'ENGR 101': set(),
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'CPSC 380': set(),
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'CPSC 406': set(),
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'CPSC 408': set()
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}
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def topological_sort(adjacency_list: dict[str, set[str]]):
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result = deque()
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visited = set()
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def dfs(current: str, visited_in_traversal=None):
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if visited_in_traversal is None:
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visited_in_traversal = set()
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if current in visited:
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return
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if current in visited_in_traversal:
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raise ValueError("Graph has a cycle")
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visited_in_traversal.add(current)
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for neighbor in adjacency_list[current]:
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dfs(neighbor, visited_in_traversal)
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# to trace the reverse path, use .append
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result.appendleft(current)
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visited.add(current)
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for node in adjacency_list.keys():
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if node not in visited:
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dfs(node)
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return result
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print(topological_sort(classes))
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