Getting input directly into a vector in C++

Question

Consider the following code piece:

...
int N,var;
vector nums;
cin >> N;
while (N--)
{
   cin >> var;
   nums.push_back(var);
}
...
         


        

Answer 1

If you don't have already copy_n() in your toolbelt then you should. Very useful.

template
Out copy_n(In first, In last, Size n, Out result)
{
    while( n-- > 0 && first != last )
        *result++ = *first++;
    return result;
}

With this utility it's convenient and elegant to copy n elements into a vector:

#include
#include
#include

// ...
int n = 0;
std::cin >> n;
std::vector v(n);
copy_n(std::istream_iterator(std::cin), std::istream_iterator(),
       n,
       v.begin());