Best way to split a vector into two smaller arrays

Question

I'm attempting to divide a vector into two distinct arrays. A text file's current int vector has one element per line. There is a list of random integers in the text file.

How I intend to approach it:

Right now, I'm thinking of making two ordinary int arrays, iterating over the whole vector, and copying n/2 elements to each array.

What I want to know is:

What is the classiest way to complete my task? I believe I can accomplish this without repeatedly iterating over the vector.

#include <vector>
#include <fstream>
#include <iterator>
#include <iostream>
using namespace std;

vector<int> ifstream_lines(ifstream& fs)
{
  vector<int> out;
  int temp;
  while(fs >> temp)
  {
    out.push_back(temp);
  }
  return out;
}

vector<int> MergeSort(vector<int>& lines)
{
  int split = lines.size() / 2;
  int arrayA[split];
  int arrayB[split];
}

int main(void) 
{
  ifstream fs("textfile.txt");
  vector<int> lines;
  lines = ifstream_lines(fs);

  return 0;
}