Ways to copy a vector in C++

There are different ways to copy a vector in C++.

1) std::copy

std:: copy is inbuilt to copy the elements from one vector to another.

Syntax

std::copy(first_iterator_o, last_iterator_o, back_inserter()):
first_iteratot_0 = First iterator of first vector.
last_iteratot_0 = Last iterator of first vector.
back_inserter() = To insert values from back.

Algorithm

Begin
   Declare v1 of vector type.
      Initialize some values into v1 vector in array pattern.
   Declare v2 of vector type.
   Call copy(v1.begin(), v1.end(), back_inserter(v2)) to copy all
   elements of v1 to v2.
   Print “v1 vector elements are :”.
   for (int i=0;i<1.size; i++)
      print the all element of v2 vector.
   Print “v2 vector elements are :”.
   for (int i=0;i<2.size; i++)
      print the all element of v2 vector.
End.

Example Code

#include<iostream>
#include<vector>
#include<algorithm> // for copy.
#include<iterator> // for back_inserter
using namespace std;
int main() {
   vector<int> v1{ 7, 6, 4, 5 };
   vector<int> v2;
   copy(v1.begin(), v1.end(), back_inserter(v2));
   cout << "v1 vector elements are : ";
   for (int i=0; i<v1.size(); i++)
      cout << v1[i] << " ";
      cout << endl;
      cout << "v2 vector elements are : ";
   for (int i=0; i<v2.size(); i++)
      cout << v2[i] << " ";
      cout<< endl;
   return 0;
}

Output

v1 vector elements are : 7 6 4 5
v2 vector elements are : 7 6 4 5

2) assign operator

This is also used to copy values from vector 1 to vector 2.

Syntax

std::assign(first_iterator_o, last_iterator_o):
first_iteratot_0 = First iterator of first vector.
last_iteratot_0 = Last iterator of first vector.

Algorithm

Begin
   Initialize a vector v1 with its elements.
   Declare another vector v2.
   Call assign() to copy the elements of v1 to v2.
   Print the elements of v1.
   Print the elements of v2.
End.

Example Code

#include<iostream> #include<vector> // for vector #include<iostream>
#include<vector>// for vector
#include<algorithm>// for copy() and assign()
#include<iterator>// for back_inserter
using namespace std;
int main() {
   vector<int> v1{7,6,4,5};
   vector<int> v2;
   v2.assign(v1.begin(), v1.end());
   cout << "v1 vector elements are : ";
   for (int i=0; i<v1.size(); i++)
      cout << v1[i] << " ";
      cout << endl;
      cout << "v2 vector elements are : ";
   for (int i=0; i<v2.size(); i++)
      cout << v2[i] << " ";
      cout<< endl;
   return 0;
}

Output

v1 vector elements are : 7 6 4 5 v2 vector elements are : 7 6 4 5

3) By assignment “=” operator

It is a simple way to copy values from vector 1 to vector 2

Algorithm

Begin
   Initialize a vector v1 with its elements.
   Declare another vector v2.
   Call assignment operator “=” to copy the elements of v1 to v2.
   Print the elements of v1.
   Print the elements of v2.
End.

Example Code

#include<iostream>
#include<vector> // for vector
#include<algorithm>// for copy() and assign()
#include<iterator>// for back_inserter
using namespace std;
int main() {
   vector<int> v1{7,6,4,5};
   vector<int> v2;
   v2 = v1 ;
   cout << "v1 vector elements are : ";
   for (int i=0; i<v1.size(); i++)
      cout << v1[i] << " ";
      cout << endl;
      cout << "v2 vector elements are : ";
   for (int i=0; i<v2.size(); i++)
      cout << v2[i] << " ";
      cout<< endl;
   return 0;
}

Output

v1 vector elements are : 7 6 4 5
v2 vector elements are : 7 6 4 5

4) By push_back method

Algorithm

Begin
   Initialize a vector v1 with its elements.
   Declare another vector v2.
   Make a for loop to copy elements of first vector into second vector by Iterative method using push_back().
   Print the elements of v1.
   Print the elements of v2.
End.

Example Code

#include<iostream> #include<vector> // for vector
#include<iostream>
#include<vector>// for vector
#include<algorithm>// for copy() and assign()
#include<iterator>// for back_inserter
using namespace std;
int main() {
   vector<int> v1{7,6,4,5};
   vector<int> v2;
   for (int i=0; i<v1.size(); i++)
      v2.push_back(v1[i]);
      cout << "v1 vector elements are : ";
   for (int i=0; i<v1.size(); i++)
      cout << v1[i] << " ";
      cout << endl;
      cout << "v2 vector elements are : ";
   for (int i=0; i<v2.size(); i++)
      cout << v2[i] << " ";
      cout<< endl;
   return 0;
}

Output

v1 vector elements are : 7 6 4 5
v2 vector elements are : 7 6 4 5

5) By passing vector as constructor

Algorithm

Begin
   Initialize a vector v1 with its elements.
   Declare another vector v2 and copying elements of first vector to second vector using constructor method and they are deeply copied.
   Print the elements of v1.
   Print the elements of v2.
End.

Example Code

#include<iostream>
#include<vector>// for vector
#include<algorithm>// for copy() and assign()
#include<iterator>// for back_inserter
using namespace std;
int main() {
   vector<int> v1{7,6,4,5};
   vector<int> v2(v1);
   cout << "v1 vector elements are : ";
   for (int i=0; i<v1.size(); i++)
      cout << v1[i] << " ";
      cout << endl;
      cout << "v2 vector elements are : ";
   for (int i=0; i<v2.size(); i++)
      cout << v2[i] << " ";
      cout<< endl;
   return 0;
}

Output

v1 vector elements are : 7 6 4 5
v2 vector elements are : 7 6 4 5