35 lines
689 B
Ruby
35 lines
689 B
Ruby
# Union-find algorithm (weighted quick-union implementation),
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# the worst case order of growth is log N,
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# see examples in test/union_find_test.rb
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class UnionFind
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attr_accessor :ids
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def initialize(count)
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@ids = [*0..count-1]
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@sizes = Array.new(count, 1)
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end
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def connected?(id1, id2)
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find(id1) == find(id2)
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end
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def find(id)
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id = @ids[id] while id != @ids[id]
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id
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end
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def union(id1, id2)
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root1 = find(id1)
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root2 = find(id2)
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return if root1 == root2
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if @sizes[root1] < @sizes[root2]
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@ids[root1] = root2
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@sizes[root2] += @sizes[root1]
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else
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@ids[root2] = root1
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@sizes[root1] += @sizes[root2]
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end
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end
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end
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