Return an array in c++

Question

Suppose I have an array

int arr[] = {...};
arr = function(arr);

I have the function as

 int& function(int arr[])
 {
//         


        

Answer 1

if not necessary, don't use it. you can just pass a reference of an array, such as:

void foo(std::vector &v) {
    for (int i = 0; i < 10; ++ i) {
        v.push_back(i);
    }
}

if you use:

std::vector foo() {
    std::vector v;
    for (int i = 0; i < 10; ++ i)
        v.push_back(i);

    return v;
}

there'll be a copy process of the container, the cost is expensive.

FYI: NRVO maybe eliminate the cost