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=begin
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File: graph_dfs.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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### 深度優先走訪輔助函式 ###
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def dfs(graph, visited, res, vet)
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res << vet # 記錄訪問頂點
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visited.add(vet) # 標記該頂點已被訪問
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# 走訪該頂點的所有鄰接頂點
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for adj_vet in graph.adj_list[vet]
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next if visited.include?(adj_vet) # 跳過已被訪問的頂點
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# 遞迴訪問鄰接頂點
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dfs(graph, visited, res, adj_vet)
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end
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end
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### 深度優先走訪 ###
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def graph_dfs(graph, start_vet)
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# 使用鄰接表來表示圖，以便獲取指定頂點的所有鄰接頂點
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# 頂點走訪序列
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res = []
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# 雜湊集合，用於記錄已被訪問過的頂點
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visited = Set.new
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dfs(graph, visited, res, start_vet)
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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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# 初始化無向圖
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v = vals_to_vets([0, 1, 2, 3, 4, 5, 6])
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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[2], v[5]],
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[v[4], v[5]],
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[v[5], v[6]],
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]
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graph = GraphAdjList.new(edges)
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puts "\n初始化後，圖為"
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graph.__print__
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# 深度優先走訪
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res = graph_dfs(graph, v[0])
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puts "\n深度優先走訪（DFS）頂點序列為"
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p vets_to_vals(res)
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end
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