format_table.rb

def format_as_table(header, data)
  total_columns = data.first.size
  data.insert(0, header) if header
  column_widths = total_columns.times.map { |col| data.map { |row| row[col].size }.max }
  if header
    data.insert(1, Array.new(total_columns, '-').zip(column_widths).map { |a, b| a * b })
  end
  data.map do |row|
    row.zip(column_widths).map do |cell, width|
      cell.to_s.ljust(width)
    end.join(" | ")
  end.join("\n")
end