Hash Challenge

example.rb

hash = { 
  a: 1,
  b: 2, 
  c: { 
    d: 3, 
    e: { 
      f: 4 
    }, 
    g: 5
  }
}

# some function like flatten_hash(hash) should return [:a, :b, :c, :d, :e, :f, :g]

flatten_hash_1.rb

def flatten_hash(hash)
  arr = []
  hash.each do |k, v|
    arr << k
  end
  arr
end

flatten_hash_2.rb

def flatten_hash(hash)
  arr = []
  hash.each do |k, v|
    if v.is_a?(Hash)
      v.each do |k2, v2|
        arr << k2
      end
    end
    arr << k
  end
  arr
end

flatten_hash_3.rb

def flatten_hash(hash)
  arr = []
  hash.each do |k, v|
    if v.is_a?(Hash)
      v.each do |k2, v2|
        if v2.is_a?(Hash)
          v2.each do |k3, v3|
            arr << k3
          end
        end
        arr << k2
      end
    end
    arr << k
  end
  arr
end

flatten_hash_4.rb

def flatten_hash(hash, arr=[])
  hash.each do |k, v|
    if v.is_a?(Hash)
      flatten_hash(v, arr)
    end
    arr << k
  end
  arr
end

flatten_hash_spec.rb

describe "FlattenHash" do
  it "returns an array of keys for a nested hash" do
    expected = [:a, :b, :c, :d, :e, :f, :g]
    actual = flatten_hash(hash)
    expect(actual).to match_array(expected)
  end
end