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51 lines
1.3 KiB
Python
51 lines
1.3 KiB
Python
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def strongly_connected_components(graph):
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index_counter = 0
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stack = []
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lowlinks = {}
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index = {}
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result = []
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def strongconnect(node, index_counter):
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index[node] = index_counter
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lowlinks[node] = index_counter
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index_counter += 1
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stack.append(node)
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try:
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successors = graph[node]
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except:
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successors = []
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# Depth first search
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for successor in successors:
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# Does the current node point to a node that was already
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# visited?
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if successor not in lowlinks:
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# Successor has not yet been visited; recurse on it
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strongconnect(successor, index_counter)
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lowlinks[node] = min(lowlinks[node],lowlinks[successor])
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elif successor in stack:
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# the successor is in the stack and hence in the
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# current strongly connected component (SCC)
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lowlinks[node] = min(lowlinks[node],index[successor])
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# If `node` is a root node, pop the stack and generate an SCC
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if lowlinks[node] == index[node]:
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connected_component = []
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while True:
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successor = stack.pop()
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connected_component.append(successor)
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if successor == node: break
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component = tuple(connected_component)
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# storing the result
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result.append(component)
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for node in graph:
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if node not in lowlinks:
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strongconnect(node, index_counter)
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return result
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