数组在while循环中没有正确初始化

Array not initializing properly within a while loop

本文关键字：初始化 while 循环 数组      更新时间：2023-10-16

我的问题是，我已经设置了一个数组来存储从文件中读取的值计算出来的总数。然后将这些存储的总数加在一起，得出总体平均值。

这个问题是由程序开头的一个'cin'引起的，用户输入一个数字，这个数字应该通过设置程序循环的次数和数组内有多少个模块来驱动程序。不管我怎么努力，这个数组似乎都不能正常工作。

#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
using namespace std;
int main()
{
    string StudentGrades;
    int studentID;
    double quiz1;
    double quiz2;
    double quiz3;
    double quiz4;
int total = 0;
double choice;
ofstream outFile;
double numStud=1;
cout << "Enter student ID number, Quiz 1 Grade, Quiz 2 Grade , Quiz 3 Grade, Quiz 4 Grade" << endl;
outFile.open("StudentGrades.txt");
cout << "How many students would you like to enter?" << endl;
cin >> numStud;
for (int x = 0; x < numStud; x++)
{
    cout << "Enter student ID: ";
    cin >> studentID;
    cout << "Enter quiz grade 1: ";
    cin >> quiz1;
    //cout << quiz1;
    cout << "Enter quiz grade 2: ";
    cin >> quiz2;
    //cout << quiz2;
    cout << "Enter quiz grade 3: ";
    cin >> quiz3;
    //cout << quiz3;
    cout << "Enter quiz grade 4: ";
    cin >> quiz4;
    //cout << quiz4;
    cout << endl;
    //outFile.open("StudentGrades.txt");
    if (outFile.is_open())
    {
        cout << "inside if/else outFile" << endl;
        //outFile << "File successfully open";
        outFile << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
    }
    else
    {
        cout << "Error opening file";
    }
    outFile.close();
    /*cout << "Enter 0 for no more students. Enter 1 for more students." << endl;
    cin >> choice;
    if (choice == 1)
        continue;
    if (choice == 0)
    {
        outFile.close();
        break;
    }*/
}

ifstream inFile;
inFile.open("StudentGrades.txt");
int sTotal;
int total[numStud];
while (inFile >> studentID >> quiz1 >> quiz2 >> quiz3 >> quiz4)
{
    //cout << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
    total = (quiz1 + quiz2 + quiz3 + quiz4);
    sTotal = total[numStud];
    double avg = total / 4;

}

system("pause");
return 0;

}

int total[numStud];是一个可变长度数组，在c++中不是标准的。如果你需要一个数组，你不知道它的大小，那么你应该使用std::vector。vector几乎可以完全像数组一样使用。例如，你可以变成:

int total;
std::vector<int> studentTotal;
while (inFile >> studentID >> quiz1 >> quiz2 >> quiz3 >> quiz4)
{
    //cout << studentID << " " << quiz1 << " " << quiz2 << " " << quiz3 << " " << quiz4 << endl;
    studentTotal.push_back(quiz1 + quiz2 + quiz3 + quiz4); // insert into the vector at the end
    total += studentTotal.back();  // get last inserted element
}
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