STL-Vector in C++ Programming

Vector is a template class in STL (Standard Template Library) of C++ programming language. The vectors are sequence containers that store elements.

Syntax :
vector < type parameter > vector_name ;

The program demonstrates the use of the STL vector container in C++. First, the program creates an empty vector a.

array < int > a ;

The program then uses various member functions of the vector container to manipulate and display its contents

The capacity() function is used to determine the current capacity of the vector.
The push_back() function is used to add elements to the back of the vector.
The size() function is used to determine the current size of the vector.
The at() function is used to access an element at a specific index.
The front() and back() functions are used to access the first and last elements of the vector respectively.
The pop_back() function is used to remove the last element of the vector.
The clear() function is used to remove all elements from the vector.
The program also demonstrates the creation of a vector b with a specified size and initial value using the constructor vector(size, value) .
The program also demonstrates the creation of a vector c by copying the contents of vector b.
The begin() and end() functions are used to iterate over the elements of the vector using a loop.
The swap() function is used to swap the contents of vectors c and d.

#include<iostream>
#include<vector>
using namespace std;
//STL-Vector in C++
int main()
{
    vector<int> a;
    cout<<"Capacity : "<<a.capacity()<<endl;
    a.push_back(10);
    cout<<"Capacity : "<<a.capacity()<<endl;
    a.push_back(20);
    cout<<"Capacity : "<<a.capacity()<<endl;
    a.push_back(30);
    cout<<"Capacity : "<<a.capacity()<<endl;
    cout<<"Size : "<<a.size()<<endl;
    cout<<"Vector Element At 2 Index : "<<a.at(2)<<endl;
    cout<<"Vector First Element: "<<a.front()<<endl;
    cout<<"Vector Last Element: "<<a.back()<<endl;
    cout<<"Before Pop : "<<endl;
    cout<<"A : ";
    for(int x : a)
    {
        cout<<" "<<x;
    }
    cout<<endl;
    a.pop_back();
    cout<<"After Pop : "<<endl;
    cout<<"A : ";
    for(int x : a)
    {
        cout<<" "<<x;
    }
    cout<<endl;
    cout<<"Before Size : "<<a.size()<<endl;
    a.clear();
    cout<<"After Size : "<<a.size()<<endl;
    cout<<"After Capacity : "<<a.capacity()<<endl;
 
    vector<int> b(5,10);
    cout<<"B : ";
    for(int x : b)
    {
        cout<<" "<<x;
    }
    vector<int> c(b);
    cout<<endl;
    cout<<"C : ";
    for(int x : c)
    {
    cout<<" "<<x;
    }
     cout <<endl;
  for (auto i = c.begin(); i != c.end(); i++)
    cout << *i << " ";
 
     vector<int> d(5,20);
     cout<<endl;
    cout<<"C : ";
    for(int x : c)
    {
        cout<<" "<<x;
    }
    cout<<endl;
    cout<<"D : ";
    for(int x : d)
    {
        cout<<" "<<x;
    }
 
     c.swap(d);
 
    cout<<endl;
    cout<<"C : ";
    for(int x : c)
    {
        cout<<" "<<x;
    }
    cout<<endl;
    cout<<"D : ";
    for(int x : d)
    {
        cout<<" "<<x;
    }
 
    return 0;
}

Output

Capacity : 0
Capacity : 1
Capacity : 2
Capacity : 4
Size : 3
Vector Element At 2 Index : 30
Vector First Element: 10
Vector Last Element: 30
Before Pop :
A :  10 20 30
After Pop :
A :  10 20
Before Size : 2
After Size : 0
After Capacity : 4
B :  10 10 10 10 10
C :  10 10 10 10 10
10 10 10 10 10
C :  10 10 10 10 10
D :  20 20 20 20 20
C :  20 20 20 20 20
D :  10 10 10 10 10

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