Vector

#include<iostream>
#include<vector>

using namespace std;
int main()
{

vector<int>v;                                               //declaring vector v

vector<int> a(5,1);                                        //another method of initializing the vector(here vector a is of size 5 nd all elements are initialized by 1)

vector<int> xyz(a);                                        //to copy all elements of vector a 
cout<<"print xyz"<<endl;
for(int i:xyz)
{
cout<<i<<" ";
}cout<<endl;

cout<<"Capacity-->"<<v.capacity()<<endl;                   //capicity finds the memory allowcated to vector v

v.push_back(1);                                            //to enter the elements to a vector from back
cout<<"Capacity-->"<<v.capacity()<<endl;

v.push_back(2);
cout<<"Capacity-->"<<v.capacity()<<endl;

v.push_back(3);
cout<<"Capacity-->"<<v.capacity()<<endl;                         ------OUTPUT----- Capacity-->4
cout<<"Size-->"<<v.size()<<endl;                                 ------OUTPUT----- Size-->3

cout<<"Element at 2nd Index-->"<<v.at(2)<<endl;             //print the element at index 2
cout<<"Empty or not-->"<<v.empty()<<endl;                   //tells whether a vector is empty or not(0-false;1-true)
                                                                    
cout<<"First element-->"<<v.front()<<endl;                  //prints the first element of a vector
cout<<"Last element-->"<<v.back()<<endl;                    //prints the last element of a vector

cout<<"before pop"<<endl;
for(int i:v)
{
cout<<i<<" ";
}cout<<endl;

v.pop_back();                                               //to remove one element from the last
cout<<"after pop"<<endl;
for(int i:v)
{
cout<<i<<" ";
}

cout<<"Before clear size "<<v.size()<<endl;
v.clear();                                                  //to remove all elements from vector v(but it's size becames 0 not capacity: Capacity remains as it is)
cout<<"After clear size "<<v.size()<<endl;

------------------------OUTPUT----------------------
print xyz
1 1 1 1 1
Capacity-->0
Capacity-->1
Capacity-->2
Capacity-->4
Size-->3
Element at 2nd Index-->3
Empty or not-->0
First element-->1
Last element-->3
before pop
1 2 3 
after pop
1 2 
Before clear size 2
After clear size  0