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* Revised the book * Update the book with the second revised edition * Revise base on the manuscript of the first edition
64 lines
1.8 KiB
Python
64 lines
1.8 KiB
Python
"""
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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
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from pathlib import Path
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sys.path.append(str(Path(__file__).parent.parent))
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from modules import Vertex, vals_to_vets, vets_to_vals
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from collections import deque
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from graph_adjacency_list import GraphAdjList
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def graph_bfs(graph: GraphAdjList, start_vet: Vertex) -> list[Vertex]:
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"""广度优先遍历"""
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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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# 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[Vertex]([start_vet])
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# 队列用于实现 BFS
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que = deque[Vertex]([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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"""Driver Code"""
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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 = [
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[v[0], v[1]],
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[v[0], v[3]],
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[v[1], v[2]],
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[v[1], v[4]],
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[v[2], v[5]],
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[v[3], v[4]],
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[v[3], v[6]],
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[v[4], v[5]],
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[v[4], v[7]],
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[v[5], v[8]],
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[v[6], v[7]],
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[v[7], v[8]],
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]
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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
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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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