How can I declare an array inside a function according to the size of a parameter?

Question

Here is what I have tried:

int fun1(vector s)
{ 
    const int n = s.size();
    int arr[n]; //<----want to declare an array of length s.size()         


        

Answer 1

Declaring array by int arr[N]; the size N must be determined in compile-time (except for some compiler extensions which allow you to define them in run-time too). By the way, you can make it:

std::unique_ptr arr (new int [n]);

// ... or ...

std::vector arr(n);