C ++如何计算文件中的范围等级

Question

下午好，我想说这是我使用C ++的第一学期，因此我很抱歉，如果遇到的错误的答案很明显/很容易就可以解决。

我正在尝试实现一个程序，该程序向用户请求文件，该文件包含学生的一系列成绩（共20个）。该程序要求用户输入传统字母等级的范围输入（即A = 90-100，B = 80-89，C = 70-79，以此类推至F），然后计算用户输入文件中等级的数量提供。

到目前为止，我的程序循环遍历每个字母等级以收集用户的等级范围，但是在计算文件中的等级数时遇到了问题。它会一直输出“此范围内的成绩数是29。”

（请注意，我的代码还会根据文件中每个年级的已记数生成一个直方图。显然，由于我的提示功能需要一些修正，因此我的直方图输出目前看起来非常笨拙。）

再次对此表示歉意，如果答案很简单。我对此很陌生，正在学习。谢谢阅读。

#include "SFML/Graphics.hpp"
#include <iostream>
#include <fstream>
#include <string>

const float WIDTH     = 550.0;     // width of the window for display
const float HEIGHT    = 750.0;     // height of the window for display
const int   FONT_SIZE   =  25;     // character size
const float LEFT_X    = 100.0;     // Left X position for label
const float LOW_Y     = 700.0;     // LOW  Y position for label
const float HIGH_Y    =  50.0;     // HIGH Y position for label

using namespace std;




void readConfig() {
    int numGrades = 5;
    int maxInGrade = 20;
    string filename;

    cout << "Enter the number of possible different grades: " << endl;
    cin >> numGrades;

    cout << "Enter the maximum number of students receiving the same letter grade: " << endl;
    cin >> maxInGrade;

    cout << "Enter the filename containing the scores: " << endl;
    cin >> filename;
}

void initFrequency() {
    string letters;
    int numGrades = 5;
    int freqLetters, low, high;
    //below defines the lowest range for each grade
    int grade_range_a = 90;
    int grade_range_b = 80;
    int grade_range_c = 70;
    int grade_range_d = 60;
    int grade_range_f = 0;



    cout << "For each grade enter the" << endl << endl
         << "(1) string representing the grade," << endl
         << "(2) lowest possible score in that range, and" << endl
         << "(3) highest possible score in that range." << endl;

    ifstream infile("/Users/quinntortellini/CLionProjects/cop3014-p7-f18/cop3014-p8-f18-attempt2/resources/hist.in");
    if(!infile)
    {
        cout << "Can't open file hist.in";
        exit(EXIT_FAILURE);
    }

    int sum=0, number;

    for (int i=0; i<numGrades; i++)
    {
        cout << "Grade string: " << endl;
        cin >> letters;
        cout << "Lowest possible score: " << endl;
        cin >> low;
        cout << "Highest possible score: " << endl;
        cin >> high;
        cout << "The number of grades in this range is " << endl;

        while (infile >> low)
        {
            if (low == grade_range_a||grade_range_b||grade_range_c||grade_range_d||grade_range_f);
            counter = counter += 1;
        }
        {
            cout << counter << endl;
        }
        infile.close();
    }

}

int main() {

    int numGrades  = 5;   // number of different letter grades
    int maxInGrade = 20;  // maximum number of students in any letter grade
    string filename;      // name of input file containing scores

    // 
    // implementing readConfig, initializes numGrades, maxInGrade, and
    //                                        filename
    //

    readConfig();

    string letters[numGrades];   // each entry represents string representing the grade
    int freqLetters[numGrades];  // each entry records occurrence of grades corresponding
    // to the letter grade

    initFrequency();

    //
    //
    //
    sf::RenderWindow window(sf::VideoMode(600, 800), "COP3014 Grade Histogram");
    sf::Font font;
    font.loadFromFile("resources/arial.ttf");

    // You are free to change the following code. However, as it is, it should work
    sf::Text min, max;
    min.setFillColor(sf::Color::Yellow);
    min.setFont(font);
    min.setString("0");
    min.setCharacterSize(FONT_SIZE);
    max.setFillColor(sf::Color::Yellow);
    max.setFont(font);
    max.setString(to_string(maxInGrade));
    max.setCharacterSize(FONT_SIZE);
    min.setPosition(LEFT_X-FONT_SIZE*2, LOW_Y-FONT_SIZE);
    max.setPosition(LEFT_X-FONT_SIZE*2, HIGH_Y-FONT_SIZE/2);

    sf::RectangleShape bars[numGrades];
    sf::Text labels[numGrades];

    float x_incr = (WIDTH - 100)/numGrades;
    float x_offset = LEFT_X+FONT_SIZE;
    float height_unit_pixels = (HEIGHT - (HIGH_Y + FONT_SIZE)) / maxInGrade;

    int count = 0;
    for (int i=0; i < numGrades; i++) {
        float height = freqLetters[i] > maxInGrade ? maxInGrade : freqLetters[i];
        bars[i].setSize(sf::Vector2f(x_incr-50, height*height_unit_pixels));
        bars[i].setPosition(x_offset+x_incr/2, LOW_Y);
        bars[i].rotate(180);
        labels[i].setFillColor(sf::Color::Yellow);
        labels[i].setFont(font);
        labels[i].setString(letters[i]);
        labels[i].setCharacterSize(FONT_SIZE);
        labels[i].setFillColor(sf::Color::Red);
        labels[i].setPosition(bars[i].getPosition().x-FONT_SIZE, LOW_Y+FONT_SIZE);
        x_offset += x_incr;
    }

    while (window.isOpen()) {
        sf::Event event;

        while (window.pollEvent(event)) {
            switch (event.type) {
                case sf::Event::Closed:
                    window.close();
                    break;
                default:
                    window.clear();
                    window.draw(min);
                    window.draw(max);

                    for (int i = 0; i < numGrades; i++) {
                        window.draw(bars[i]);
                        window.draw(labels[i]);
                    }
                    window.display();
            }
        }
    }
    return 0;
}