Class SparseVector
    attr_reader :vector

    def initialize(h = {})
        @vector = Hash.new(0)
        @vector = @vector.merge!(h)
    end

    def [](i)
        @vector[i]
    end

    def to_s
        @vector.to_s
    end
end

class SparseMatrix

    attr_reader :matrix

    def initialize(h = {})
        @matrix = Hash.new({})
        for k in h.keys do
            @matrix[k] = if h[k].is_a? SparseVector
            h[k]
        else
            @matrix[k] = SparseVector.new(h[k])
        end
    end
end

    def [](i)
        @matrix[i]
    end

    def col(j)
        c = {}
        for r in @matrix.keys do
            c[r] = @matrix[r].vector[j] if
@matrix[r].vector.keys.include? j
        end
        SparseVector.new c
    end
end

hsh = SparseMatrix.new 1 => {1 => 33, 2 => 44, 3 => 55}, 2 => {1 => 66,
3 => 77}
puts hsh[1][3]
puts hsh.col(2)

That's the code I have, I need to know if I can if I can get the indexes
of the hash looping through the hash.
I've tried using each-do, but i couldn't make it work.
I need to do this so that I can operate with Sparse Matrices and Dense
Matrices.

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