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=begin
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File: graph_bfs.rb
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Created Time: 2024-04-25
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Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
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=end
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require 'set'
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require_relative './graph_adjacency_list'
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require_relative '../utils/vertex'
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### 广度优先遍历 ###
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def graph_bfs(graph, start_vet)
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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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# 哈希集合，用于记录已被访问过的顶点
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visited = Set.new([start_vet])
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# 队列用于实现 BFS
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que = [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 que.length > 0
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vet = que.shift # 队首顶点出队
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res << 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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next if visited.include?(adj_vet) # 跳过已被访问的顶点
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que << 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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end
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end
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# 返回顶点遍历序列
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res
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end
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### Driver Code ###
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if __FILE__ == $0
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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.new(edges)
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puts "\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.first)
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puts "\n广度优先便利（BFS）顶点序列为"
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p vets_to_vals(res)
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end
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