gistfile1.rb

# 输入一个数组，表示每种书买本书，例如 [1,2,0,0,0] 是第一集买一本、第二集买两本
def book_price(order)
  price = [0, 1 * 100, 0.95 * 200, 0.9 * 300, 0.8 * 400, 0.75 * 500 ]
  order = order.reject{ |x| x <= 0 }

  if order.size == 0
    return 0
  else
    kind = order.count{ |x| x > 0 }
    min_size = order.min

    return book_price(order.map{ |x| x - min_size }) + (price[kind] * min_size)
  end
end

describe "Book price" do

  it [1,0,0,0,0] do
    result = book_price([1,0,0,0,0])
    expect(result).to eq(100)
  end

  it [1,1,0,0,0] do
    result = book_price([1,1,0,0,0])
    expect(result).to eq(190)
  end

  it [1,1,1,0,0] do
    result = book_price([1,1,1,0,0])
    expect(result).to eq(270)
  end

  it [1,1,1,1,0] do
    result = book_price([1,1,1,1,0])
    expect(result).to eq(320)
  end

  it [1,1,1,1,1] do
    result = book_price([1,1,1,1,1])
    expect(result).to eq(375)
  end

  it [2,1,1,1,1] do
    result = book_price([2,1,1,1,1])
    expect(result).to eq(475)
  end

  it [3,1,1,1,1] do
    result = book_price([3,1,1,1,1])
    expect(result).to eq(575)
  end

  it [2,2,1,1,1] do
    result = book_price([2,2,1,1,1])
    expect(result).to eq(565)
  end

  it [3,2,1,1,1] do
    result = book_price([3,2,1,1,1])
    expect(result).to eq(665)
  end

  it [2,2,2,1,1] do
    result = book_price([2,2,2,1,1])
    expect(result).to eq(645)
  end

  it [2,2,2,2,1] do
    result = book_price([2,2,2,2,1])
    expect(result).to eq(695)
  end

  it [2,2,2,2,2] do
    result = book_price([2,2,2,2,2])
    expect(result).to eq(750)
  end

  it [3,2,2,2,2] do
    result = book_price([3,2,2,2,2])
    expect(result).to eq(850)
  end

end