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Copy a vector to another in C++

C++ vector copy programs: Here, we are going to learn how to copy a vector to another? Here, we are using two different ways to copy one vector to another?
Submitted by IncludeHelp, on September 27, 2018

The ways that we are using to copy vectors in C++, are:

1. Copy one vector's elements to another (Simple approach)
2. Copy vector by using an assignment operator
3. Copy vector 1 to vector 2 while declaring vector 2 by passing the first vector as an argument (parameterized constructor)

1) Copy one vector’s elements to another (Simple approach)

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

int main()
{

	//declar and initialize vector 1
	vector<int> v1{10,20,30,40,50};
	//declare vector2
	vector<int> v2;
	
	//copy v2 to v1
	for(int i=0; i<v1.size(); i++){
		v2.push_back(v1[i]);
	}
	
	//printing v1 and v2
	cout<<"v1 elements: ";
	for(int i=0; i<v1.size(); i++){
		cout<<v1[i]<<" ";
	}
	cout<<endl;

	cout<<"v2 elements: ";
	for(int i=0; i<v2.size(); i++){
		cout<<v2[i]<<" ";
	}
	cout<<endl;	
	
	return 0;
}

Output

v1 elements: 10 20 30 40 50
v2 elements: 10 20 30 40 50

2) Copy vector by using an assignment operator

Syntax:

 v2 = v1;

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

int main()
{

	//declar and initialize vector 1
	vector<int> v1{10,20,30,40,50};
	//declare vector2
	vector<int> v2;
	
	//copying v1 to v2
	v2 = v1;
	
	//printing v1 and v2
	cout<<"v1 elements: ";
	for(int i=0; i<v1.size(); i++){
		cout<<v1[i]<<" ";
	}

	cout<<endl;
	cout<<"v2 elements: ";
	for(int i=0; i<v2.size(); i++){
		cout<<v2[i]<<" ";
	}
	cout<<endl;	
	
	return 0;
}

Output

v1 elements: 10 20 30 40 50
v2 elements: 10 20 30 40 50

3) Copy vector 1 to vector 2 while declaring vector 2 by passing the first vector as an argument (parameterized constructor)

Syntax:

 vector<int> v2(v1);

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

int main()
{
	//declar and initialize vector 1
	vector<int> v1{10,20,30,40,50};
	//declare vector2 by copying vector1
	vector<int> v2(v1);
	
	//printing v1 and v2
	cout<<"v1 elements: ";
	for(int i=0; i<v1.size(); i++){
		cout<<v1[i]<<" ";
	}
	cout<<endl;
	cout<<"v2 elements: ";
	for(int i=0; i<v2.size(); i++){
		cout<<v2[i]<<" ";
	}
	cout<<endl;	
	
	return 0;
}

Output

v1 elements: 10 20 30 40 50
v2 elements: 10 20 30 40 50