Vectors in C++

                                                                                 

While programming use of arrays is very common and almost everyone even the beginner knows about it. Now we know that array is a contiguous memory location of fixed size . Here the problem begins that we cannot increase the size of an array later during run time thus we need to declare a very large array and a lot of memory is wasted . So here is the solution , Vectors in simple terms are expandable arrays . Not talking much let's get straight to an example .

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here we are creating a vector named v1 of integer type (surely you can go for any data type ) then we inserted 3 integers from the end then i show usage of various functions . After clearing next we insert two more integers so first we had the size 3 and now we have size 2 that means flexible size . Also we can directly acess any element by writing v1[index]

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C++ Program :

 /* vector in common language is a expandable array with large number of functionalities */  
 #include <iostream>  
 #include <vector>  
 using namespace std;  
 int main ()  
 {  
  vector<int> v1;  
  int sum=0 ,i;  
  v1.push_back (1);  
  v1.push_back (2);  
  v1.push_back (3);  
  cout<<"\n second element is "<<v1[1]<<"\n";  
  while (!v1.empty())  
  {  
   sum+=v1.back();  
   v1.pop_back();  
  }  
  cout << "The elements of v1 add up to " << sum << '\n';  
  v1.clear();  
  v1.push_back (1101);  
  v1.push_back (2202);  
  cout << "v1 contains:";  
  for ( i=0; i<v1.size(); i++)  
    cout << ' ' << v1[i];  
   cout << '\n';  
 }  

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        And here is the output