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47 lines
939 B
Python
47 lines
939 B
Python
"""
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BFS.
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pseudo-code:
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BFS(graph G, start vertex s):
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// all nodes initially unexplored
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mark s as explored
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let Q = queue data structure, initialized with s
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while Q is non-empty:
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remove the first node of Q, call it v
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for each edge(v, w): // for w in graph[v]
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if w unexplored:
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mark w as explored
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add w to Q (at the end)
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"""
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G = {
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"A": ["B", "C"],
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"B": ["A", "D", "E"],
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"C": ["A", "F"],
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"D": ["B"],
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"E": ["B", "F"],
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"F": ["C", "E"],
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}
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def bfs(graph, start):
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"""
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>>> ''.join(sorted(bfs(G, 'A')))
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'ABCDEF'
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"""
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explored, queue = set(), [start] # collections.deque([start])
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explored.add(start)
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while queue:
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v = queue.pop(0) # queue.popleft()
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for w in graph[v]:
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if w not in explored:
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explored.add(w)
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queue.append(w)
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return explored
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if __name__ == "__main__":
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print(bfs(G, "A"))
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