Question

这看起来很简单，但我在这里遗漏了一些东西以使这段代码有效。我要做的是用学生的数字，身份，分数和名字打印25行4列的二维数组内容。
当我用数字初始化数组时，我尝试了类似于这段代码的东西。但是现在我正在从文件中读取数据，我已经碰到了墙，需要帮助。
我尝试在cin对象中使用数组的名称，但我收到如下错误消息：

＆＃34; assign6.cpp：49：11：错误：不匹配＆＃39;运算符＆gt;＆gt;＆＃39; （操作数类型是＆＃39; std :: ifstream {aka std :: basic_ifstream}＆＃39; const int（*）[4]＆＃39;）＆＃34; < / p>

所以我把它拿出来，现在代码编译但是我得到了垃圾。有什么建议？很抱歉没有尽快回来。我陷入其他任务中。我做了更改，现在程序正常运行。结果如下。

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

 using namespace std;

 //const
 const int Array_Row = 25;
 const int Array_Col = 4;

 //arrays
 string letterGrade[Array_Row];
 int myScores[Array_Row][Array_Col];
  string names[Array_Row];


 int main()
 {
 int count;
 //int average;

 ifstream  inFile;
 inFile.open("classData.txt");

 int arraySize = 0;

 if(inFile.is_open())
 {
 int counter = 0;
 while(inFile.eof()==false)
 {

 inFile >> myScores[counter][0];
 inFile >> myScores[counter][1];
 inFile >> myScores[counter][2];
inFile >> myScores[counter][3];
getline(inFile, names[counter]); 
 counter++;
 }
 }else

 cout << "Failed";

 for(int counter = 0; counter < Array_Row-2; counter++)
 {

 for(int index = 0; index < Array_Col; index++)
 {
  cout << setw(4) << fixed;
  cout << myScores[counter][index];

 }
 cout << names[counter] << endl;
 }
 inFile.close();

 for(int counter = 0; counter < Array_Row-2; counter++)
 {  

 cout << setprecision(2) << setw(2) << fixed;
 double studentAverage = (myScores[counter][0] + myScores[counter][1] +     myScores[counter][2] + myScores[counter][3])/4.0;
  cout << "Student average is ";
  cout << studentAverage;
  cout << " ......" <<names[counter] << endl;

 if(studentAverage >=90.00)
 letterGrade[counter] = "A";
 else if(studentAverage >=80.00 && studentAverage<=89.99)
 letterGrade[counter] = "B";
 else if(studentAverage >=70.00 && studentAverage<=79.99)
 letterGrade[counter] = "C";
else if(studentAverage >=60.00 && studentAverage<=69.99)
letterGrade[counter] = "D";
else if(studentAverage <59)
letterGrade[counter] = "F";
cout << "Student letter grade is: "<< letterGrade[counter] << endl;

}

double classAverage = 0;
for(int counter = 0; counter < Array_Row-2; counter++)
 {  
      classAverage += (myScores[counter][0] + myScores[counter][1] +     myScores[counter][2] + myScores[counter][3]);
}

     cout << "Class average is : "<< (classAverage/92.0);//calculate class average



    int test1Total = 0;
    for(int index = 0; index <Array_Row-2; index++)
    test1Total += myScores[index][0];
    int test1Average = (test1Total/23.0); //calculates test1 average


       cout <<"\nStudent average for test 1: "  << test1Average <<   setprecision(2) <<fixed;

     int test2Total = 0;
     for(int index = 0; index <Array_Row-2; index++)
     test2Total += myScores[index][1];
     int test2Average = (test2Total/23.0); 
      cout <<"\nStudent average for test 2: "  << test2Average;//calculates test2 average

      int test3Total = 0;
      for(int index = 0; index <Array_Row-2; index++)
      test3Total += myScores[index][2];
       int test3Average = (test3Total/23.0); 
        cout <<"\nStudent average for test 3: "  << test3Average;//calculates  test3 average


      int test4Total = 0;
      for(int index = 0; index <Array_Row-2; index++)
       test4Total += myScores[index][3];
      int test4Average = (test4Total/23.0); 
         cout <<"\nStudent average for test 4: "  << test4Average;//calculates test4 average



   return 0;
}

Answer 1

我找不到您发布的错误，但代码问题是getline(...)函数。

这是getline的原型： istream& getline (istream& is, string& str);

如您所见，它会返回istream，您无法将其传递给<<运算符。你能做的是：

string str;
getline(inFile, name) >> str;

然后打印：

cout << "The numbers are"
     << myArray[count][index]
     << str << endl;

Answer 2

此声明中有错误

cout << "The numbers are"
     << myArray[count][index]
     << getline(inFile,name) << endl;

运营商＆gt;＆gt;从左到右执行。所以首先输出到cout

cout << "The numbers are"

然后你发送给cout未初始化的myArray值[count] [index]

<< myArray[count][index]

之后

<< getline(inFile,name) << endl;

另外，使用getline时出错。如果您的输入文件只包含空格分隔的int值，那么正确的版本是

inFile >> myArray[count][index];
cout << "The numbers are"
     << myArray[count][index] << endl;

将二维数组传递给数据文件中的函数并输出内容

2 个答案: