Question

Consider the following code piece:

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

Is it possible to do this without using an auxillary variable, in this case var?

Answer 1

Assuming you have already read the initial N, there is a nice trick using istream_iterator:

std::vector<int> nums;
nums.reserve(N);
std::copy(std::istream_iterator<int>(std::cin), 
          std::istream_iterator<int>(),
          std::back_inserter(nums));

The back_inserter object turns itself into an iterator that adds elements to the vector at the end. Iterator streams can be parameterized by the type of the elements read, and, if no parameter given, signals the end of input.