从文本中读取数字并输出平均值

Question

所以我正在努力从文件中读取文本（逐行）并输出ID，ID 之后的平均 4 个等级，以及字母等级。因此，任何平均成绩为 50 或以上的字母等级为 S，任何低于 50 的字母为 U，而 2 个免责课程的字母等级为 I。 （如果超过或等于 2，则没有 S 或 U）。

假设文件有数字：

42 50 51 57 52
48 90 -1 60 -1
40 46 -1 59 45
47 50 -1 49 50

输出应该是这样的：

ID=42 Avg=52.5 Grade=S
ID=48 Excused=2 Grade=I
ID=40 Avg=50.0 Grade=S
ID=47 Avg=49.7 Grade=U

类型的等级数

S    U    I
2    1    1

This is the output I am receiving from my code

它正在读取所有数字，但我需要它来读取第一个数字为ID，然后读取 4 个数字作为等级。

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

using namespace std;

int main()
{
    ifstream in;
    ofstream results;
    string filename;
    char grade;
    int S = 0, U = 0, I = 0, i = 0, ID, excused = 0, avg;
    double allscores = 0;

    cout << "Enter the name of the file that has the scores of students: " << endl;
    cin >> filename;

    cout << "Enter the number of scores for each student: " << endl;
    cin >> ID;

    in.open(filename);
    results.open("results.txt");

    if (in)
    {
        while (in >> ID)
        {
            int first = 0

            for (i = 0; i<=4; i++)
            {
                if (first == -1)
                    excused++;
                else
                    allscores += first;
            }
            if (first > 4)
            {
                avg = allscores / (4 - excused);

                if (avg >= 50.0)
                {
                    grade = 'S';
                    S++;
                    cout << "ID=" << ID << " Avg=" << avg << " Grade =" << grade << endl;

                }
                else
                {
                    grade = 'U';
                    U++;
                    cout << "ID=" << ID << " Avg=" << avg << " Grade =" << grade << endl;
                }
            }

            else
            {
                grade = 'I';
                I++;
                cout << "ID=" << ID << " Excused=" << excused << " Grade =" << grade << endl;
            }
        }
    }
    else
    {
        cout << "Couldn't open file\n";
    }

    cout << "Number of Grades of Type" << endl;
    cout << "S   " << "U   " << "I" << endl;
    cout << S << "   " << U << "   " << I << endl;

    in.close();
    results.close();

    system("pause");
    return 0;
}

Answer 1

您的变量 int first=0 在您的代码中没有被分配除 0 以外的任何值，因此语句 if(first>4) 将始终为 false 并导致您得到的输出。

你可以这样做：

    while (in >> ID)//this is supposed to get the ID of each student, in order for that to happen you need to read all the 4 scores inside this loop before coming here and reading the next ID,otherwise everything will read as an ID
    {
       int first = 0
       excused=0;//you need to reset excused on every iteration
       allscores=0;//you need to reset allscore on every iteration
       for (i = 0; i<4; i++)
       {//here you need to get all the 4 scores
           in>>first;//get each score in first
           if (first == -1)
             excused++;
           else
             allscores += first;
       }

       if(excused<2)//instead of if(first>4)
            ...//do your calculation for average score
       else
            ...//set the grade to 'I'...
    }

Answer 2

这是我的最终解决方案：

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

using namespace std;

int main()
{
    ifstream in;
    ofstream results;
    string filename;
    char grade;
    int S = 0, U = 0, I = 0, i = 0, ID, excused = 0, avg;
    double allscores = 0;

    cout << "Enter the name of the file that has the scores of students: " << endl;
    cin >> filename;

    cout << "Enter the number of scores for each student: " << endl;
    cin >> ID;

    in.open(filename);
    results.open("results.txt");

    if (in)
    {
        while (in >> ID)
        {
            int first = 0;
            excused = 0;
            allscores = 0;
            for (i = 0; i < 4; i++)
            {
                in >> first;
                if (first == -1)
                    excused++;
                else
                    allscores += first;
            }

            if (excused < 2)
            {
                avg = allscores / (4 - excused);

                if (avg >= 50.0)
                {
                    grade = 'S';
                    S++;
                    results << "ID=" << ID << " Avg=" << avg << " Grade =" << grade << endl;

                }
                else
                {
                    grade = 'U';
                    U++;
                    results << "ID=" << ID << " Avg=" << avg << " Grade =" << grade << endl;
                }
            }
            else
            {
                grade = 'I';
                I++;
                results << "ID=" << ID << " Excused=" << excused << " Grade =" << grade << endl;
            }
        }
    }

    else
    {
        cout << "Couldn't open file\n";
    }

    results << "Number of Grades of Type" << endl;
    results << "S   " << "U   " << "I" << endl;
    results << S << "   " << U << "   " << I << endl;

    in.close();
    results.close();

    system("pause");
    return 0;
}

在代码之后，我将其输出到名为“results”的文件中。
谢谢您的帮助。我猜我的 while 循环是最大的错误。
特别是不要添加in >> first 部分。