VECTORS

First of all include the header #include<vector> in file;

The capacity of the vector at the time it is initialised is 0,

when value is stored in it, its capacity first increases by 1 and

then gets doubled each time the capacity of the vector lacks.

Vector <datatype> vector_name; //creates vector of size zero.

Vector <datatype> vector_name(n);//creates vector of size n.

vector_name.push_back(any number);//to insert any number in the vector and the value gets inserted in the one by one order.

vector_name.pop_back();  //pops out the last element from the vector.

This function does not reduces the size of the vector once increased by push_back() function.

To enter the elmts in vector with help of loop.

for(i=0; i<n; i++)

{

cin>>a;

vector_name.push_back(a);

}

vector_name.size(); // returns the number of elements filled in vector.

vector_name.capacity(); //returns the capacity of the vector.

vector_name.clear(); // is used to empty the vector.

We can also sort the vector as follows;

vector<datatype>v_name;

sort(v_name.begin(),v_name.end());

ex- In this we have sorted the vector in ascending order and printed

it with help of iterator.

int main() 

{ 

    vector<int> v{ 1, 5, 8, 9, 6, 7, 3, 4, 2, 0 }; 

    sort(v.begin(), v.end()); 

    cout << "Sorted \n"; 

     vector<int>::iterator ptr; 

     for(ptr=v.begin();ptr<v.end();ptr++)

     cout<<*ptr;

Or

for(int i=0;i<v.size();i++)

cout<<v[i];

     return 0; 

} 

use sort(v.begin(), v.end(),greater<int>());  // to sort the vector in

descending order.

To compare two vectors.

#include<bits/stdc++.h>

using namespace std;

// Check if all elements is equal or not

int main()

{

  // Comparing equal vectors

  vector<int> v1{3, 1, 2, 3};

  vector<int> v2{3, 1, 2, 3};

  (v1 == v2)?  cout << "Equal\n" : cout << "Not Equal\n";

    

  // Comparing non-equal vectors

  vector<int> v3{1, 2, 3, 4};

  (v1 == v3)?  cout << "Equal\n" : cout << "Not Equal\n";

    

  // comparing with empty

  vector<int> v4;

  (v1 == v4)?  cout << "Equal\n" : cout << "Not Equal\n";

  

  // comparing two empty

  vector<int> v5;

  (v5 == v4)?  cout << "Equal\n" : cout << "Not Equal\n";

  

   return 0;

}

output:

Equal

Not Equal

Not Equal

Equal