C++ array (Beginner) - c++

Question

I misstook arrays for vectors, Sorry (array is vektor in swedish)
I would need some help with a program I'm making. It is a assignment so I really need to understand how I do this and not just get the code :P
I need to make a array containing 10 "numbers" (I would like to make them editable when the program is running).
After I'v done this I need to make the program calculate the "average value" of all the numbers "/
Would be pretty neat if you could pick how many numbers you wanted the average value of as well, if anyone could share some knowledge in how I should to that :P
Anyways, I'v tried some code to make the vector that didn't work, I might as well add it here:
int vector[10];
and
vector[0] "number 1: ";
and so on for the input of numbers in the vector.
int sum = vector[0] + vector[1] + ...
cout << "average value is: " << sum/5;
should work for getting the average value though (right?)
I should allso add:
float average(int v[], int n)
to this thing as well, can't really se how though.
Any help/knowledge at all would be awesome! Cheers.

Answer 1

To pick how many numbers you wanted to average:
Native: (G++/Clang) only, not "legal" C++
cin >> num;
int vector[num];
"Correct" native (pointers):
int *vector = new int [num];
"Proper" C++:
#include <vector>
std::vector<int> v(num);

Answer 2

A function like following would work for computing average of an array containing n elements.
float average(int v[], int n)
{
float sum = 0;
for(int i = 0 ; i < n ; i++)
{
sum += v[i]; //sum all the numbers in the vector v
}
return sum / n;
}
You can declare your array as you have done however i do recommend you to name it something else then vector to avoid confusion. About tour issue with changing the numbers in the array you can do this by for example maning a loop going from one to 10 and then make the user enter values for all the fields.
Vektor på svenska = array på engelska (vector är något annat :))

Answer 3

If you want exactly 10 numbers, you can eliminate a lot of overhead by simply using an array. However, assuming you want to use a vector, you can easily find the average taking advantage of its "size" member, as such:
float average(std::vector<int> nums)
{
int sum = 0;
for (unsigned int i = 0; i < nums.size(); i++)
sum += nums[i];
return sum / nums.size();
}
Note that this does assume the sum won't be higher than 2^31-1, IE the highest number a signed integer can represent. To be safer you could use an unsigned and/or 64 bit int for sum, or some arbitrary precision library like gmp, but I'd assume that is all outside the scope of your assignment.

Answer 4

You must declare and array of size 10, which you have done.
Use a loop to get ten inputs from the user.
(for or while loops would do)
Use another loop to calculate the sum of all ten numbers and store it in a variable.
Divide the variable by ten.
This is what you need to do essentially. But, to make your driver program prettier, you can define the following functions:
void GetInput(int *A); //put the input loop here
You can also write any one of the given two functions:
long Sum(int * A) //put the summing loop here
double Average(int * A) //put the summing loop here AND divide the sum by ten
Since you are a beginner I feel obliged to tell you that you don't need to return an array since it isalways passed as a reference parameter. I did not bother to pass the array size as a parameter to any functions because that is fixed and known to be 10 but it will be good practice to do that.