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56 lines
1.3 KiB
Python
56 lines
1.3 KiB
Python
# Finding Articulation Points in Undirected Graph
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def compute_ap(graph):
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n = len(graph)
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out_edge_count = 0
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low = [0] * n
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visited = [False] * n
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is_art = [False] * n
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def dfs(root, at, parent, out_edge_count):
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if parent == root:
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out_edge_count += 1
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visited[at] = True
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low[at] = at
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for to in graph[at]:
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if to == parent:
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pass
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elif not visited[to]:
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out_edge_count = dfs(root, to, at, out_edge_count)
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low[at] = min(low[at], low[to])
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# AP found via bridge
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if at < low[to]:
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is_art[at] = True
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# AP found via cycle
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if at == low[to]:
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is_art[at] = True
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else:
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low[at] = min(low[at], to)
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return out_edge_count
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for i in range(n):
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if not visited[i]:
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out_edge_count = 0
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out_edge_count = dfs(i, i, -1, out_edge_count)
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is_art[i] = out_edge_count > 1
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for x in range(len(is_art)):
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if is_art[x] is True:
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print(x)
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# Adjacency list of graph
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graph = {
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0: [1, 2],
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1: [0, 2],
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2: [0, 1, 3, 5],
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3: [2, 4],
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4: [3],
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5: [2, 6, 8],
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6: [5, 7],
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7: [6, 8],
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8: [5, 7],
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}
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compute_ap(graph)
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