How does a vector work in C++?

Vectors have the ability to resize itself automatically like dynamic arrays when an element is inserted or deleted, the container handle their storage automatically. Vector elements are placed in contiguous storage so that they can be accessed and traversed using iterators. Data can be inserted or erased at the begin, middle or end of the vector.

This is a C++ program to implement various functions of the vector.

Algorithm

Begin
   Declare a variable v of vector type.
   Declare another variable it as iterator of vector type.
   Declare another two variable c and i to the ineger datatype.
   while (1) do
      print “1.Size of the Vector”.
      print “2.Insert Element into the Vector”.
      print “3.Delete Last Element of the Vector”.
      print “4.Resize the vector”.
      print “5.Reserve the vector”.
      print “6.Display the capacity of vector”.
      print “7.Display by Iterator”.
      print “8.Clear the Vector”.
      print “9.Exit”.
      print “Enter your Choice:”.
      Enter the value of variable c.
      Switch(c)
         Case 1.
            Print “Size of Vector:”.
            Call size() function to print the size of the
            vector.
            Break.
         Case 2.
            Print “Enter value to be inserted:”.
            Enter the value of variable i.
            Call push_back() function to input the values in the
            vector.
            Break.
         Case 3.
            Print “Delete Last Element Inserted:”.
            Call pop_back() function to delete the values in
            the vector.
            Break.
         Case 4.
            Print “Resize the vector elements:”.
            Call resize() function to resize the vector.
            Break.
         Case 5.
            Print “Reserve the vector elements:”.
            Call reserve() function to reserve the size of
            the vector.
            Break.
         Case 6.
            Print “Displaying capacity of vector:”.
            Call capacity() function to display the capacity
            of the vector.
            Break.
         Case 7.
            Print “Displaying Vector by Iterator:”.
            for (it = v.begin(); it != v.end(); it++)
               print the value of iterator it.
            Break.
         Case 8.
            Call clear() function to clear the vector.
            Print “Vector Cleared”.
            break
         case 9.  
            call exit() function to take exit.  
            break.
         Default.
            Print “Wrong choice”.
End.

Example Code

#include <iostream>
#include <vector>
using namespace std;
int main() {
   vector<int> v;
   vector<int>::iterator it;
   int c, i;
   while (1) {
      cout<<"1.Size of the Vector"<<endl;
      cout<<"2.Insert Element into the Vector"<<endl;
      cout<<"3.Delete Last Element of the Vector"<<endl;
      cout<<"4.Resize the vector"<<endl;
      cout<<"5.Reserve vector"<<endl;
      cout<<"6.Display the capacity of vector"<<endl;
      cout<<"7.Display by Iterator"<<endl;
      cout<<"8.Clear the Vector"<<endl;
      cout<<"9.Exit"<<endl;
      cout<<"Enter your Choice: ";
      cin>>c;
      switch(c) {
         case 1:
            cout<<"Size of Vector: ";
            cout<<v.size()<<endl;
         break;
         case 2:
            cout<<"Enter value to be inserted: ";
            cin>>i;
            v.push_back(i);
         break;
         case 3:
            cout<<"Delete Last Element Inserted:"<<endl;
            v.pop_back();
         break;
         case 4:
            cout<<"Resize the vector elements:"<<endl;
            v.resize(10);
         break;
         case 5:
            cout<<"Reserve the vector elements:"<<endl;
            v.reserve(100);
         break;
         case 6:
            cout<<"Displaying capacity of vector: ";
            cout<<v.capacity()<<endl;
         break;
         case 7:
            cout<<"Displaying Vector by Iterator: ";
            for (it = v.begin(); it != v.end(); it++) {
               cout<<*it<<" ";
            }
            cout<<endl;
         break;
         case 8:
            v.clear();
            cout<<"Vector Cleared"<<endl;
         break;
         case 9:
            exit(1);
         break;
         default:
            cout<<"Wrong Choice"<<endl;
      }
   }
   return 0;
}

Output

1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 1
Size of Vector: 0
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 2
Enter value to be inserted: 1
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 2
Enter value to be inserted: 3
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 2
Enter value to be inserted: 2
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 2
Enter value to be inserted: 4
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 2
Enter value to be inserted: 5
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 2
Enter value to be inserted: 6
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 2
Enter value to be inserted: 7
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 2
Enter value to be inserted: 8
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 2
Enter value to be inserted: 9
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 2
Enter value to be inserted: 10
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 2
Enter value to be inserted: 11
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 2
Enter value to be inserted: 12
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 1
Size of Vector: 12
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 7
Displaying Vector by Iterator: 1 3 2 4 5 6 7 8 9 10 11 12
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 4
Resize the vector elements:
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 7
Displaying Vector by Iterator: 1 3 2 4 5 6 7 8 9 10
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 3
Delete Last Element Inserted:
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 7
Displaying Vector by Iterator: 1 3 2 4 5 6 7 8 9
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 8
Vector Cleared
1.Size of the Vector
2.Insert Element into the Vector
3.Delete Last Element of the Vector
4.Resize the vector
5.Reserve vector
6.Display the capacity of vector
7.Display by Iterator
8.Clear the Vector
9.Exit
Enter your Choice: 9