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"""
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File: graph_bfs.py
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Created Time: 2023-02-23
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Author: Krahets (krahets@163.com)
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"""
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import sys, os.path as osp
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sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
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from include import *
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from graph_adjacency_list import GraphAdjList
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""" 广度优先遍历 BFS """
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# 使用邻接表来表示图，以便获取指定顶点的所有邻接顶点
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def graph_bfs(graph: GraphAdjList, start_vet: Vertex) -> List[Vertex]:
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# 顶点遍历序列
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res = []
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# 哈希表，用于记录已被访问过的顶点
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visited = set([start_vet])
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# 队列用于实现 BFS
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que = collections.deque([start_vet])
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# 以顶点 vet 为起点，循环直至访问完所有顶点
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while len(que) > 0:
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vet = que.popleft() # 队首顶点出队
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res.append(vet) # 记录访问顶点
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# 遍历该顶点的所有邻接顶点
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for adj_vet in graph.adj_list[vet]:
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if adj_vet in visited:
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continue # 跳过已被访问过的顶点
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que.append(adj_vet) # 只入队未访问的顶点
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visited.add(adj_vet) # 标记该顶点已被访问
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# 返回顶点遍历序列
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return res
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if __name__ == "__main__":
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"""初始化无向图"""
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v = vals_to_vets([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
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edges = [[v[0], v[1]], [v[0], v[3]], [v[1], v[2]], [v[1], v[4]],
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[v[2], v[5]], [v[3], v[4]], [v[3], v[6]], [v[4], v[5]],
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[v[4], v[7]], [v[5], v[8]], [v[6], v[7]], [v[7], v[8]]]
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graph = GraphAdjList(edges)
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print("\n初始化后，图为")
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graph.print()
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"""广度优先遍历 BFS"""
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res = graph_bfs(graph, v[0])
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print("\n广度优先遍历（BFS）顶点序列为")
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print(vets_to_vals(res))
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