54 lines
942 B
Ruby
54 lines
942 B
Ruby
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require 'set'
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# Depth-first search to find paths in an undirected graph.
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# The graph is represented as an adjacency list of Integers,
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# see examples in test/dfs_test.rb
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class DFS
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class Graph
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attr_accessor :size, :adj
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def initialize(size)
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@size = size
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@adj = Array.new(size) { Set.new }
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end
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def add_edge(v, w)
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@adj[v].add(w)
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@adj[w].add(v)
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end
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end
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def initialize(graph, source)
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@graph = graph
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@source = source
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@edge_to = Array.new(graph.size, nil)
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@visited = Array.new(graph.size, false)
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search(source)
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end
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def path_to(v)
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return nil unless @visited[v]
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path = []
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w = v
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while w != @source
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path.push(w)
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w = @edge_to[w]
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end
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path.push(@source)
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path.reverse
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end
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private
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def search(v)
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@visited[v] = true
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@graph.adj[v].each do |w|
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next if @visited[w]
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@edge_to[w] = v
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search(w)
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end
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end
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end
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