Introduction 

  • In this article you will get the knowledge of vectors in c++.

  • The points that are covered in this article are mention below.

  • What is a vector and why we use in C++?
  • Important function used in vector?
  • How do I get the size of a vector in C++?
  • How do you add an element to a vector in C++?
  • How do you find the last element of a vector?
  • Sorting a vector in descending order in C++?
  • Can you have a vector of vectors C++?
  • vector c++ examples.?
  • Vector pointer in c++.?
  • vector constructor in c++?
  • some problems   in vector ? 

Vectors in c++

Vectors in c++



What is vector and why we use in c++


  • vector is a dynamic contiguous array and it is a sequence container(linear fashion).
  • In vector we insert as many elements we want to add but in a array  of 10 integer to add the 11th element we need to make an array again.
  • it is likely to array but array has static data type and vector has dynamic datatype.
  • vector is declared in the header file (#include<vector>).
  • we use vector in c++ because it is dynamic and it automatically adjust the size when an element is inserted or deleted from it.


Important functions used mostly in vector


 How do I get values in vector in C++

   1.  push_back(add elements in the add of vector)
           syntax -
                vec1.push_back(39);


 How do I delete last element in vector in C++


         2. pop_back (delete the last element)

             syntax -
                    vec1.pop_back(  )
   

 How do I erase a vector in C++

      3. erase (This is used to erase the elements in the vector)

            syntax-
                vec1.erase(vec1.begin()+3)This will erase 4th element from first



 How do I begin a vector in C++


   4.begin() (This is used to begin from the first element)
          
          syntax-
               vec1.begin()
    


  How do I get the size of a vector in C++

        5. size() (This function help us to get the size of the vector)
   
              syntax-
                         vec1.size()


 How do I insert  an element in vector in C++

   
  6.  insert() (This function is used to insert value in vector)
         
          syntax-
              vector<int>::iterator it;
        vec1.insert(it,5);


How do I access the front element in vector in C++


   7. front() (This function help us to access the first element of vector)
 
          syntax-
                   vec1.front()


How do I access the back element in vector in C++


   7. back() (This function help us to access the first element of vector)
 
          syntax-
                   vec1.back()


How do I copy of element in vector in C++


   8. insert() (This function is used to insert value in vector)
         
          syntax-
              vector<int>::iterator it;
        vec1.insert(it+1,5);  //number of element you its copy will print



 How do I sort an element in vector in C++

         9. sort() (This function is used to sort value in vector)
         
          syntax-
               sort()
                     sort(vec1.begin(),vec1.end())

           for descending order 

                          sort(vec1.rbegin(),vec1.rend())


    For more functions   click here 



Coding 

#include <iostream>

#include <vector>

#include <algorithm>

using namespace std;


  • This is the required header files here we will use vectors so we include here <vector>
  • header file and for using some sorting and some data structure functions we use here
  • <algorithm> header file.


int main()

{

   //ways to create vector


    vector<int> vec1;        //zero length integer vector

    int element, size ;

     cout<<"Enter the size of your vector"<<endl;

     cin>>size;

     for (int i = 0; i < size; i++)

     {

         cout<<"Enter an element to add to this vector";

         cin>>element;

         vec1.push_back(element);

     }


  • This is the way to create a vector and add value to insert it .first create a 
  • zero length vector ,then declare two variables of element and size for storing 
  • the size of vector and elements in vector  and use vec1.push_back for storing our elements in vector.



void display(vector<T> &v)

{

    cout<<"Displaying this vector";

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

    {

        cout << v[i] << " ";

        cout << v.at(i) << " "; //at operator help us to know where is the value

    }

    cout << endl;

}


This is the way to create a function of name display to display the elements in vector.



 vec1.pop_back();

display(vec1);


This is the way to remove value from last using pop_back function and display this using the display function.



vector<int>::iterator it;

vec1.insert(it,5);


This is the way to insert element into vector using iterator and  display it through the function display().


erasing element from the vector


vec1.erase(vec1.begin()+3);//this will erase the 4th element


vec1.erase(vec1.begin(), vec1.begin()+3);//This will erase the 1st 3 element



This is the way to erase elements in the vector


sort(vec1.begin(), vec1.end()); //for sorting the vectors

 cout << "The elements after sorting in the vector is::" << endl;

 for (int i = 0; i < vec1.size(); i++)

 {

  cout << vec1[i] << " \n";

 }


This is the way to sort the  elements in the vector



for (int i = 0; i < vec1.size(); i++)

    {

        cout << vec1[i] << " \n";

    }

    return 0;

}


Lastly display the size of the vector and display it.



Coding Execution in IDE


#include <iostream>

#include <vector>

#include <algorithm>

using namespace std;

int main()

{

    vector<int> vec1;

    int element, size;

    cout << "Enter the size of the vector:" << endl;

    cin >> size;

    for (int i = 0; i < size; i++)

    {

        cout << "Enter the element To add In vector:" << endl;

        cin >> element;

         vec1.push_back(element);

    }

  //using itarator  insert the element This is always tuse an iterator

//   vector<int>::iterator it;

//     vec1.insert(it,5);


 //erasing element from the vector

//   vec1.erase(vec1.begin()+3);//this will erase the 4th element

//   vec1.erase(vec1.begin(), vec1.begin()+3);//This will erase the 1st 3 element

    // sort(vec1.begin(), vec1.end()); //for sorting the vectors

    // cout << "The elements after sorting in the vector is::" << endl;

    // for (int i = 0; i < vec1.size(); i++)

    // {

    //     cout << vec1[i] << " \n";

    // }

//   vec1.push_back(78);

//   vec1.push_back(16);

//   // now front equals 78, and back 16

//   vec1.front() -= vec1.back();

    //if try to remove the element

    // vec1.pop_back();

    //  cout << "After pop back the elements are:"<<endl;

    for (int i = 0; i < vec1.size(); i++)

    {

        cout << vec1[i] << " \n";

    }

    return 0;

}



vector pointer in c++

#include <iostream>

#include <vector>

using namespace std;

void foo(vector<int>* a) ///else we can use here reference &a

{

    cout << a->at(0) << a->at(1) << a->at(2) << endl;

    // expected result is "123"

}

int main()

{

    vector<int> a;

    a.push_back(1);

    a.push_back(2);

    a.push_back(3);

    foo(&a);

}



This is an example  of pointer using in vector .



vector constructor in c++

#include <iostream>

#include <vector>

#include <algorithm>

using namespace std;

int main()

{

    vector<int> first;                               //empty vector of ints

    vector<int> second(4, 100);                      //4 ints with value 100

    vector<int> third(second.begin(), second.end()); //itarating through the second vector

    vector<int> fourth(third);                       //a copy of third


    // the iterator constructor can also be used to construct from arrays:


    int myint[] = {4, 5, 6, 9};

    vector<int> fifth(myint, myint + sizeof(myint) / sizeof(int));


    cout << "The contents of fifth are:";

    for (std::vector<int>::iterator it = fifth.begin(); it != fifth.end(); ++it)

        cout << ' ' << *it;

    cout << '\n';

}

This is an example  of constructor using in vector .




Some problems  in vector

Q-1)

Prints three highest numbers from a list of numbers in descending order

Q-2)
Q-3)



Also check Out





  Q-2)  pointers in c




  

   Q-3) Vector Sort


Also check Out Projects for Resume

    click here

Projects on C++


Projects on C


Problems On C


Problems On C++



Feedback

Hope you understand all the things that are we discussed till now if still you have any doubts regarding Vectors in C++ please comment below and we will try to solve that 


THANKYOU!!