更改函数以使用向量而不是数组

Question

I'm getting a little stuck changing functions to use vectors. I've got the below function that creates a new dynamic array. Now I need to do the same but use vectors.

int *makeData(int size)
{
    int *ptr = nullptr;
    ptr = new int[size];
    return ptr;
}

This is all i got so far and can't seem to figure out what to do next. Do i need a pointer to return?

int *makeData(int size)
{
    vector<int> data(100);
}

This function seems to be okay but is there a way to optimize it (make it simpler, and cleaner).

void getMovieData2(vector<int> data, int num)
{
int temp;
cout << "Enter the number of movies each student saw.\n";

for (int count = 0; count < num; count++)
{
    cout << "Student " << (count + 1) << ": ";
    cin >> temp;
    data.push_back (temp);

    while (arr[count] <= 0)
    {
        cout << "The number of movies be greater than zero.\n";
        cout << "How many movies were seen by Student " 
             << (count + 1) << "? ";
        cin >> temp;
        data.push_back (temp);
    }
}
}

Answer 1

Using a vector has made the makeData function redundant. It doesn't do anything that simply declaring a variable of type vector doesn't already do better.

Cleaning up the other function is possible, but has nothing to do with the question about vectors.

Also, none of this has anything to do with overloading.

Answer 2

Your makeData for vectors would be

vector<int> makeData(int size) {
    return vector<int>(size);
}

As you see it is effectively the same as

vector<int> data(size);

However it can be useful if you use auto consistently

auto data = makeData(size);

As of your getMovieData function: no, that function is not working as expected. You are passing a vector as value and are "returning" data in it - except that you are putting your data into a local copy that will be destroyed when the function returns.

The solution is to use a reference, as in

void getMovieData(vector<int> &outData, int count);

However I suggest you simply return a new vector

vector<int> getMovieData(int count);

Answer 3

The capacity of vector object can be either reserved or resized. The reserve function allocates additional memory for internal storage.

While the resize function sets the size of maximum possible elements in vector.

Examples can be found here:

http://www.cplusplus.com/reference/vector/vector/resize/

http://www.cplusplus.com/reference/vector/vector/reserve/