STL : copy a vector into another vector in C++ using copy

 By using inbuilt copy functions

copy(itBegin(),it!=end(), back_inserter()) :- first way to copy old vector into new one. This function takes 3 arguments, first, the first iterator is old vector first value, second, the last iterator of old ,Last in back_inserter. Vector V2 in empty ,so we can not use V2.begin() as a target but we have to use intserter.

 

	#include<iostream>
	#include<vector>
	#include<iterator>
	using namespace std;
	int main()
	{
	vector<int>v1{1,2,3,4,5};
	vector<int>v2;
	cout<<"First vector size: "<<v1.size()<<endl;
	cout<<"Second vector size :"<<v2.size()<<endl;
	vector<int>::iterator it;
	copy(v1.begin(),v1.end(),back_inserter(v2));
	cout<<"First vector size: "<<v1.size()<<endl;
	cout<<"Second vector size :"<<v2.size()<<endl;
	cout<<"--------------First Vector-------"<<endl;
	for(auto &el : v1)
	{cout<<el<<" ";}
	cout<<endl;
	cout<<"--------------Second Vector-------"<<endl;
	for(auto it=v2.begin();it!=v2.end();it++)
	{
	cout<<*it<<" ";
	}
	return 0;
	}

view raw .cc hosted with ❤ by GitHub

First vector size: 5
First vector size: 5
Second vector size :5
--------------First Vector-------
1 2 3 4 5
--------------Second Vector-------
1 2 3 4 5

If your vector in pre initilized by some random value then you can use same above copy commend with V2.begin() inside copy.

	#include<iostream>
	#include<vector>
	#include<iterator>
	using namespace std;
	int main()
	{
	vector<int>v1{1,2,3,4,5};
	vector<int>v2(5,1);
	cout<<"First vector size: "<<v1.size()<<endl;
	cout<<"Second vector size :"<<v2.size()<<endl;
	vector<int>::iterator it;
	copy(v1.begin(),v1.end(),v2.begin());
	cout<<"First vector size: "<<v1.size()<<endl;
	cout<<"Second vector size :"<<v2.size()<<endl;
	cout<<"--------------First Vector-------"<<endl;
	for(auto &el : v1)
	{cout<<el<<" ";}
	cout<<endl;
	cout<<"--------------Second Vector-------"<<endl;
	for(auto it=v2.begin();it!=v2.end();it++)
	{
	cout<<*it<<" ";
	}
	return 0;
	}

view raw .cc hosted with ❤ by GitHub

First vector size: 5
First vector size: 5
Second vector size :5
--------------First Vector-------
1 2 3 4 5
--------------Second Vector-------
1 2 3 4 5