How to join two Arrays using STL in C++?

// C++ program to join two Arrays 
// using set_union() in STL 

#include <bits/stdc++.h> 
using namespace std; 

int main() 
{ 

  // Get the array 
  int arr1[] = { 1, 45, 54, 71, 76, 12 }; 
  int arr2[] = { 1, 7, 5, 4, 6, 12 }; 

  // Compute the sizes 
  int n1 = sizeof(arr1) / sizeof(arr1[0]); 
  int n2 = sizeof(arr2) / sizeof(arr2[0]); 

  // Sort the arrays 
  sort(arr1, arr1 + n1); 
  sort(arr2, arr2 + n2); 

  // Print the array 
  cout << "First Array: "; 
  for (int i = 0; i < n1; i++) 
    cout << arr1[i] << " "; 
  cout << endl; 

  cout << "Second Array: "; 
  for (int i = 0; i < n2; i++) 
    cout << arr2[i] << " "; 
  cout << endl; 

  // Initialise a vector 
  // to store the merged values 
  // and an iterator 
  // to traverse this vector 
  vector<int> v(n1 + n2); 
  vector<int>::iterator it, st; 

  it = set_union(arr1, arr1 + n1, 
        arr2, arr2 + n2, 
        v.begin()); 

  // Print the merged array 
  cout << "\nAfter joining:\n"; 
  for (st = v.begin(); st != it; ++st) 
    cout << *st << ", "; 
  cout << '\n'; 

  return 0; 
}