从文本文档中获取不同的数据类型并将其存储到向量中？ C++

Question

I have an assignment I am supposed to complete and really need some help with grasping and understanding certain concepts.

Basically our task is to create a document called students.txt, where we will store a bunch of student information via this format:

Example:

---

1387 History 4.0

3984 Science 2.3

---

The program will basically be able to create new students via inputting their ID, major and GPA by the user, and store it on a line underneath. I am having some issues with understanding how I would format certain things. I currently have this:

#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
using namespace std;

int main(){
   std::ofstream studentFile{ "students.txt", std::ios::app };
   int studentID;
   string major;
   double gpa;

   cout << "ID #: ";
   cin >> studentID;

  cout << "Major: ";
  cin >> major;

  cout << "GPA: ";
  cin >> gpa;

  studentFile << studentID << " ";
  studentFile << major << " ";
  studentFile << gpa << " " << endl;

  studentFile.close();

  return 0;
}

I am also concerned on how I would do a feature of the program which requires you to display the given contents of the file if the user inputs to do so. The hint is that when the program runs, the main function will have vectors, and each vector will represent each column of the document that can be used later on. This is what i cannot grasp about the program, how each vector will read and know what to store and how, so that later if the user asks to remove a student via only by their ID, the rest of the information concerning that ID will be deleted as well.

Such as: Remove student: 3984

Or when asked the user asks to display the current information on the document it shows:

3728 Biology 3.6 8372 Math 2.4 2933 Science 3.4

For the displaying part, I have this:

#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
#include <vector> 
using namespace std;

int main(){
  ifstream studentFile;
  studentFile.open("students.txt");


  vector<int> student_ids;
  std::vector<std::string> student_majors;
  vector<float> student_gpas;

  int data;

  while (studentFile >> data) {
    student_ids.push_back(data);
  }

  studentFile.close();
  cout << student_ids[0] << endl;
  cout << student_ids[1] << endl;
  cout << student_ids[2] << endl;

  return 0;
}

I know this isn't correct, but am trying to grasp how I would get data from a text document and store each data into a specific vector, so that the ID's in the document would be stored in vector student_ids, majors in the major vector etc.

Any help or tips would mean the world, thank you for your time:)

Answer 1

It's a mistake to make 3 vectors. The better way would be to produce a Student class:

class Student {
public:
     int id;
     std::string major;
     double gpa;
};

Then you can define your vector:

std::vector<Student> students;

This way, you can keep all the data about a single student in a tidy little package.

Then you need to have a for-loop that reads lines from your input file, sticks the data into a Student object, and then pushes that into the vector.

Start with this structure for your code and see if you get further.

---

However, you've talked about iterating through three vectors.

vector<int> vec1;
vector<string> vec2;
vector<double> vec3;

... Assume you populate them equally so they're all the same size

for (size_t index = 0; index < vec1.size(); ++index) {
    int thisA = vec1.at(index);
    string thisStr = vec2.at(index);
    double thisDouble = vec3.at(index);
}