title: Triangular Matchstick Number
signature: function triangular_matchstick_number(x)
source_py: def triangular_matchstick_number(x):
      return (((3 * x) * (x + 1)) / 2)
source_cpp: int triangular_matchstick_number(int x) {
    return ( 3 * x * ( x + 1 ) ) / 2;
  }
question_info.entry_fn_name: triangular_matchstick_number
question_info.entry_cls_name: Solution
question_info.test_case_ids: ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']
question_info.test_code: 
  
  -- SOLUTION CODE
  -- ============================================
  PLACEHOLDER_CODE_BODY
  
  -- TESTING CODE 
  -- ============================================
  function isCorrect(actual, expected)
      if type(expected) ~= type(actual) then
          return false
      end
      
      if type(expected) == 'table' then
          for k,v_expected in pairs(expected) do
              
              if actual[k] == nil then
                  return false
              end
              local v_actual = actual[k]
              if not isCorrect(v_actual, v_expected) then
                  return false
              end
              actual[k]=nil
          end
      
          if next(actual) then 
              return false
          end
          return true
      else
          return actual == expected
      end
  end
  
  function validateSolution(actual, expected)
      return math.abs(actual - expected) < 1e-06
  end
  
  function driver(x, expected)
      local exec_result;
      local status, error_msg = pcall(function () 
          exec_result=PLACEHOLDER_FN_NAME(x) 
      end)
      if status then
          if validateSolution(exec_result,expected) then
              return "PASSED"
          end
          return "FAILED"
      else
          return string.format("ERROR=%s",string.gsub(error_msg,".*:[%d]+: ",""))
      end
  end
      
  function main()
      result = driver(6, 63.0)
      print(string.format("TEST-0...%s",result))
  
      result = driver(25, 975.0)
      print(string.format("TEST-1...%s",result))
  
      result = driver(15, 360.0)
      print(string.format("TEST-2...%s",result))
  
      result = driver(30, 1395.0)
      print(string.format("TEST-3...%s",result))
  
      result = driver(17, 459.0)
      print(string.format("TEST-4...%s",result))
  
      result = driver(80, 9720.0)
      print(string.format("TEST-5...%s",result))
  
      result = driver(27, 1134.0)
      print(string.format("TEST-6...%s",result))
  
      result = driver(13, 273.0)
      print(string.format("TEST-7...%s",result))
  
      result = driver(12, 234.0)
      print(string.format("TEST-8...%s",result))
  
      result = driver(67, 6834.0)
      print(string.format("TEST-9...%s",result))
  
  end
  
  main()
question_info.test_list: [{"idx": 0, "outputs": 63.0, "inputs": {"x": 6}}, {"idx": 1, "outputs": 975.0, "inputs": {"x": 25}}, {"idx": 2, "outputs": 360.0, "inputs": {"x": 15}}, {"idx": 3, "outputs": 1395.0, "inputs": {"x": 30}}, {"idx": 4, "outputs": 459.0, "inputs": {"x": 17}}, {"idx": 5, "outputs": 9720.0, "inputs": {"x": 80}}, {"idx": 6, "outputs": 1134.0, "inputs": {"x": 27}}, {"idx": 7, "outputs": 273.0, "inputs": {"x": 13}}, {"idx": 8, "outputs": 234.0, "inputs": {"x": 12}}, {"idx": 9, "outputs": 6834.0, "inputs": {"x": 67}}]