该程序运行但不正确; 数字不对

Question

这个程序运行但不正确的数字不对,我从文件中读取数字,然后当我在程序中使用它们时他们是不对的.:我正在尝试做的解释可以有人告诉我,如果看起来不对.

这就是我要做的:

编写一个程序,确定100名学生的成绩分散

您要将考试成绩读入三个阵列,每个考试一个阵列.然后你必须计算得分A(90或以上),B(80或以上),C(70或以上),D(60或以上)和F(少于60)的得分数.为每个考试执行此操作并将分发写入屏幕.

    // basic file operations
    #include <iostream>
    #include <fstream>
    using namespace std;
    int read_file_in_array(double exam[100][3]);
    double calculate_total(double exam1[], double exam2[], double exam3[]); // function that calcualates grades to see how many 90,80,70,60
    //void display_totals();
    double exam[100][3];
    int main()
    {
        double go,go2,go3;
        double exam[100][3],exam1[100],exam2[100],exam3[100];
        go=read_file_in_array(exam);
        go2=calculate_total(exam1,exam2,exam3);
        //go3=display_totals();
        cout << go,go2,go3;
        return 0;
    }
    /*
    int display_totals()
    {

        int grade_total;
        grade_total=calculate_total(exam1,exam2,exam3);
        return 0;
    }   */
    double calculate_total(double exam1[],double exam2[],double exam3[])
    {
        int calc_tot,above90=0, above80=0, above70=0, above60=0,i,j, fail=0;
        double exam[100][3];
        calc_tot=read_file_in_array(exam);
        for(i=0;i<100;i++)
            {
            for (j=0; j<3; j++)
                {
                exam1[i]=exam[100][0];
                exam2[i]=exam[100][1];
                exam3[i]=exam[100][2];
                if(exam[i][j] <=90 && exam[i][j] >=100)
                    {
                    above90++;
                        {
                        if(exam[i][j] <=80 && exam[i][j] >=89)
                            {
                            above80++;
                                {
                                if(exam[i][j] <=70 && exam[i][j] >=79)
                                    {
                                    above70++;
                                        {
                                        if(exam[i][j] <=60 && exam[i][j] >=69)
                                            {
                                            above60++;
                                                {
                                                if(exam[i][j] >=59)
                                                    {
                                                    fail++;
                                                }
                                                }
                                        }
                                        }
                                }
                                }
                        }
                        }
                }
            }
        }
        return 0;
    }

    int read_file_in_array(double exam[100][3])
    {
        ifstream infile;  
        int exam1[100];
        int exam2[100];
        int exam3[100];
      infile.open("grades.txt");// file containing numbers in 3 columns
        if(infile.fail()) // checks to see if file opended
            {
            cout << "error" << endl;
            }
        int num, i=0,j=0;
        while(!infile.eof()) // reads file to end of line
          {
              for(i=0;i<100;i++) // array numbers less than 100
              {
                for(j=0;j<3;j++) // while reading get 1st array or element
                infile >> exam[i][j];
                infile >> exam[i][j];
                infile >> exam[i][j];
                cout << exam[i][j] << endl;
                    {
                        if (! (infile >> exam[i][j]) )
                        cout << exam[i][j] << endl;
                    }
              exam[i][j]=exam1[i];
              exam[i][j]=exam2[i];
              exam[i][j]=exam3[i];
              }     
        infile.close();
      }
    return 0;
    }

Answer 1

读取代码有点困难,但是当你检查分数时,你应该使用chained else if语句而不是嵌套ifs.

有点像:

if(exam[i][j] >=90 && exam[i][j] <=100)
{
     above90++;
}
else if(exam[i][j] >=80 && exam[i][j] <=89)
{
     above80++;
}
else if(...)
{...}

此外,您可能希望选择一种语法并在整个代码中与其保持​​一致,在尝试解决任何问题时,或者甚至弄清楚您在做什么,这将产生巨大的差异!不要紧,什么你去的方式尽可能多的为与它保持一致.

如果条件(parens中的表达式)为真,并且如果它为假,则语句允许您执行某些操作.

if( /* statement that evaluates to true */ )
{
     /* insert the commands you want to run when it's true here */
}
else
{
     /* insert the commands you want to run when it's false here */
}

您可以使用"其他"部分链如果语句组合在一起,这样,如果你有两个以上的可能性是非常有用的.比如这样:

int number = 2; // Can be a value between 0 and 2 (0, 1, or 2)
if(number == 0)
{
     cout << "The number is zero";
}
else if(number == 1)
{
     cout << "The number is one";
}
else if(number == 2)
{
     cout << "The number is two";
}
else
{
     cout << "The value wasn't an allowed value!";
}

如果number介于0和2之间,它将打印出它的数字,如果它不在该范围内,它将打印出一条消息,表明它不是.