Dynamic array

A dynamic array
is an array whose size can be changed during the execution of
the program. The most popular dynamic array in C++ is the
vector
structure,
which can be used almost like an ordinary array.
The following code creates an empty vector and adds three elements to it:

    vector<int> v;
    v.push_back(3); // [3]
    v.push_back(2); // [3,2]
    v.push_back(5); // [3,2,

A shorter way to iterate through a vector is as follows:
    for (auto x : v) {
        cout << x << "\n";
    }

The function back returns the last element in the vector, and the function pop_back
removes the last element 

The following code creates a vector with five elements:
    vector<int> v = {2,4,2,5,1};

Another way to create a vector is to give the number of elements and the
initial value for each element:
    // size 10, initial value 0
    vector<int> v(10);

    // size 10, initial value 5
    vector<int> v(10, 5)