C++实现浮点数输出时小数点后补两位零的问题求解

解决方案 #

你代码已经引入了格式控制所需的<iomanip>头文件，只需在文件写入逻辑前给outFile输出流设置2个格式参数即可：

• 启用fixed标记：强制使用固定小数位格式输出浮点数，关闭默认自动省略末尾小数零的逻辑
• 搭配setprecision(2)：指定固定小数位保留2位，不足位自动补零

修改步骤 #

在outFile.open("outData.txt");执行完成后、第一次向outFile写入内容前，添加如下代码即可：

outFile << fixed << setprecision(2);

该格式设置会对后续所有流向outFile的浮点数值输出生效，无需为每个输出单独配置。

修改后完整代码 #

#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>

using namespace std;

int main()
{
  ifstream inFile;
  ofstream outFile;

  string firstName, lastName, department;
  double salary, bonus, taxes;
  double distance, timeTravel;
  int coffeeCups;
  double cupCost;
  double paycheck, aveSpeed, salesAmount;

  inFile.open("inData.txt");
  outFile.open("outData.txt");

  // 新增格式控制代码
  outFile << fixed << setprecision(2);

  inFile >> firstName >> lastName >> department;
  inFile >> salary >> bonus >> taxes;
  inFile >> distance >> timeTravel;
  inFile >> coffeeCups >> cupCost;

  paycheck = salary + salary*(bonus/100) - ((salary+ salary*(bonus/100))*(taxes/100));
  aveSpeed = distance/timeTravel;
  salesAmount = coffeeCups * cupCost;

  outFile << "Name: " << firstName << " " << lastName << ", Department: " << department << endl;
 
  outFile << "Monthly Gross Salary: $" << salary << ", Monthly Bonus: " << bonus << "%" << ", Taxes: " << taxes << "%" << endl;
 
  outFile << "Paycheck: $" << paycheck << endl << endl;
 
  outFile << "Distance Traveled: " << distance << " miles, Traveling Time: " << timeTravel << " hours" << endl;
 
  outFile << "Average Speed: " << aveSpeed << " miles per hour" << endl << endl;

  outFile << "Number of Coffee Cups Sold: " << coffeeCups << ", Cost: $" << cupCost << " per cup" << endl;
 
  outFile << "Sales Amount = $" << salesAmount;

  inFile.close();
  outFile.close();
  
  return 0;
}

修改后输出的所有浮点数值都会自动保留两位小数，不足位补零，完全符合预期输出要求。

内容的提问来源于stack exchange，提问作者hannahcrow