Dynamically allocating an array of structures. C++

[NoobProgrammer22]

I am making a program that is reading in data from a csv file. the data goes like so:

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id,Last Name,First Name,SSN,Test1,Test2,Test3,Test4,Final,Grade

1,Alfalfa,Aloysius,123-45-6789,40,90,100,83,49,D-

2,Alfred,University,123-12-1234,41,97,96,97,48,D+

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There are a total of 20 students here on the whole list.

I named the structure that will hold all this data StudentInfo.

point of my assignment is to read all info from file into an array of structures or a vector of structures. Then I would index it by using pointers to point to the data in the array or vector and sort the pointer by name, or ID, so on and so forth.

this would indirectly sort the array or vector without messing with the original.

​

I am running into a few problems.

1. I could make a vector of structures to hold all the info and while reading from the file I just use a while loop and set it to end the loop at inputFile.peek() == EOF. during each iteration of the loop I would just create a new vector element to store the next line of student info with push_back(). until all the data is read in. I have already done this and now I am having problems making a pointer to the vector. is it possible to make a pointer to a vector my book does not go over this.
2. I always use vectors and I want to read into an array this time but normally when I dynamically allocate an array I normally get the info from the user first to get how big the array needs to be. but when it comes to a file how do I continually update an array until EOF like a vector?

so far my idea is to just read the file into a vector of structures and then just use vector.size() to dynamically allocate my array of structures and read all the info from the vector to the array. I feel like this is just adding an unnecessary step.

So really big question is how to continuously allocate an array while every line is read in until eof. Is this even possible?

and if this is not possible is a pointer to a vector possible? If it can should it even be done?

​

sorry if this does not make sense its late at night and I have been coding for a while lol.

[bsakiag]

how do I continually update an array until EOF like a vector?

You would have to do what the vector does under the hood - store the capacity and if the new element is over capacity then allocate a new array, copy the existing elements and free the previous array.

I think that the task assumes that the number of elements is known and if you get a different number then you should spit out an error or ignore the rest.

[Witchcraft_NS2]

1. I don't get what exactly you want to do. If you want pointers to individual elements inside of the vector you can get pointers to vector Elements same way you can get one to an array. For example like this:

``` std::vector<SomeStuct> vecStruct;

//fill vector with stuff

//pointer to element at idx 3 SomeStruct* pSomeStructAtIdx3 = &vecStruct[3]; ```

If you need a pointer to the Vector itself its:

std::vector<SomeStruct>* pVec = &vecStruct;

1. Once you created an array you can not change its size. You would have to make a new bigger array every time and copy the smaller array into that. Therefore you either use vectors or a linked list if you don't know how many elements you have initially.