Question

我正在用C ++编写一个简单的程序，它从文本文件中读取如下的示例输入：样本输入

    7 10
    William Horde AA AA AA AA AA AA AA AA AA AA ;
    John Doe AA AA AA FF AA AA AA AA AA AA ;
    Hermann Straus AA AA AA AA AA BB NA AA AA AA ;
    Patrick Doe CC CC DC CC CB CC DC CC CC CC ;
    Xhulia Abazi AA BB BB BA CB BB CB CC BB AA;
    John Trki CC BB DC DD DD DD BB AA BB CC ;
    Julien Torfelt NA FD FD DD DC DC DC DD DD ;

在第一行给出学生数0

以下是我的源代码：

#include <iostream>
#include <ofstream>

using namespace std;
void getData(char fnames[], char lnames[], string grades[], int &n, int &m);

int main()
{
    char fnames[100]; 
    char lnames[100]; 
    string grades[100]; int n,m;

    getData(fnames,lnames, grades , n, m);
    return 0;
}


void getData(char fnames[],char lnames[], string grades[], int &n, int &m)
{
    ifstream fin("input.txt");
    fin>>n; // read number of students
    fin>>m; // read number of courses
    double sum = 0.0;
    for (int i=0; i<n; i++)
    {
        fin>>fnames;
        fin>>lnames;

        for (int j=0; j<m; j++)
        {
            fin>>grades[j];
            if(grades[j]=="AA") sum = sum + 4.0;
            else if(grades[j]=="BA") sum = sum + 3.5;
            else if(grades[j]=="BB") sum = sum + 3.0;
            else if(grades[j]=="CB") sum = sum + 2.5;
            else if(grades[j]=="CC") sum = sum + 2.0;
            else if(grades[j]=="DC") sum = sum + 1.5;
            else if(grades[j]=="DD") sum = sum + 1.0;
            else if(grades[j]=="FD") sum = sum + 0.5;
            else sum = sum + 0.0; //FF , NA    
        }
    }        
}

如何让我的程序正常运行？

Answer 1

首先，有一个终止分号，你没有考虑到它。在阅读完所有成绩后，最好放弃一行中的所有内容。只需使用istream::ignore

跳过行尾即可

    // .............
        float avg = sum / m;
        cout<<"CGPA for "<<fnames<<" "<<lnames<<" is = "<<avg<<endl;; 
        fin.ignore(10, '\n');  // <------------------------------------ add this line
    }        
}

其次，您必须为每位新学生重置sum。所以将sum初始化移到学生循环中：

    fin>>n; // read number of students
    fin>>m; // read number of courses
    //double sum = 0.0;        // <------------------------------------ remove from here
    for (int i=0; i<n; i++)
    {
        double sum = 0.0;      // <------------------------------------ put here
        fin>>fnames;
        fin>>lnames;

Answer 2

代码问题是';'在文件中的行尾没有读取。

该程序未能获得';'在fin中，这样当循环继续到fin>＆gt; fnames **读取冒号，然后下一个fin继续第二行中的firstname作为lnames。

getData函数的更正代码是，

void getData(char fnames[],char lnames[], string grades[], int &n, int &m)
{
   ifstream fin("file.txt");
   char getColon[2] ; //added 
   fin>>n; // read number of students
   fin>>m; // read number of courses
   for (int i=0; i<n; i++)
   {
   double sum = 0.0;
      fin>>fnames;
      fin>>lnames;

      for (int j=0; j<m; j++)
      {
         fin>>grades[j];
         if(grades[j]=="AA") sum = sum + 4.0;
         else if(grades[j]=="BA") sum = sum + 3.5;
         else if(grades[j]=="BB") sum = sum + 3.0;
         else if(grades[j]=="CB") sum = sum + 2.5;
         else if(grades[j]=="CC") sum = sum + 2.0;
         else if(grades[j]=="DC") sum = sum + 1.5;
         else if(grades[j]=="DD") sum = sum + 1.0;
         else if(grades[j]=="FD") sum = sum + 0.5;
         else sum = sum + 0.0; //FF , NA    
      }
      fin >> getColon ; //Added 
      float avg = sum / m;
      cout<<"CGPA for "<<fnames<<" "<<lnames<<" is = "<<avg<<endl; 
   }        
}

上面代码中的行fin >> getColon ; //Added将冒号作为调整，代码流继续。

上述代码的Exact输出为，

CGPA for William Horde is = 4
CGPA for John Doe is = 3.6
CGPA for Hermann Straus is = 3.5
CGPA for Patrick Doe is = 1.95
CGPA for Xhulia Abazi is = 2.65
CGPA for Trki CC is = 1.95
CGPA for Torfelt NA is = 0.85

同样初始化第一个for循环中的sum变量，以便在计算之前为每个学生重置它。

学生评分计划C ++

2 个答案: