The vector is similar to array. 

  Vector Array
Difference It can be resized.  Size is flexible. Size is fixed.  
Declaration vector<int> v(5); int score[5];
Same -direct access

Use index [ ] to reach individual elements.
cin>>v[3];  v[2]=100;  cout<<v[2]<<" "; cin>>score[3];  score[2]=100;  cout<<score[2]<<" ";

How to create an object that is a vector?

Empty vector Five zero vector vector with different numbers
#include<iostream>
#include<vector>
using namespace std;

void main()
{
vector<int> vec;
cout<<vec.empty()<<endl;
cout<<vec.size()<<endl;
}		 #include<iostream>
#include<vector>
using namespace std;

void main()
{
vector<int> v(5); 
for(int i=0; i<v.size(); i++)
    cout<<v[i]<<" ";
cout<<endl;
}		 #include<iostream>
#include<vector>
using namespace std;

void main()
{
int A[]={3,5,6,2,1}
vector<int> w(A, A+5); 
for(int i=0; i<w.size(); i++)
    cout<<w[i]<<" ";
cout<<endl;
}

How to resize a vector?

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

void main()
{
	vector<int> vec;
	vec.resize(10);
	for(int i=0; i<vec.size(); i++)
		cout<<vec[i]<<" ";
	cout<<endl;

	vec.resize(4);
	for(i=0; i<vec.size(); i++)
		cout<<vec[i]<<" ";
	cout<<endl;

	vec.resize(6,9);
	for(i=0; i<vec.size(); i++)
		cout<<vec[i]<<" ";
	cout<<endl;
}
 Note:
1.  Create an empty vector:
        vector<int> vec;


2.  Expand the vector into 10 elements of zero:
       vec.resize(10);


3.  Shrink the vector into 4 elements (cut the end):
      vec.resize(4);


4.  Expand the vector into 6 elements with filling 9 into additional spaces.
      vec.resize(6,9);

 

How to update the end of vector?

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

void main()
{
	vector<int> vec;
	vec.push_back(8);
	vec.push_back(10);
	vec.push_back(12);
	for(int i=0; i<vec.size(); i++)
		cout<<vec[i]<<" ";
	cout<<endl;

	vec.pop_back();
	for(i=0; i<vec.size(); i++)
		cout<<vec[i]<<" ";
	cout<<endl;

	cout<<vec.back()<<endl;
}

 

 Note:
1.  Create an empty vector:
        vector<int> vec;

2. Add an element, 8, to the back of array:
       vec.push_back(8);
3.  Add an element, 10, to the back of array:
       vec.push_back(10);
4.  Add an element, 12, to the back of array:
       vec.push_back(12);

5.  Delete the last element:
      vec.pop_back();

6.  Get the content of the last element without updating the vector.
      cout<<vec.back()<<endl;