C++ Standard Template Library (STL) vector class example

This C++ program illustrates how to use the Standard Template Library (STL) vector class



#include < vector >

#include < iostream >

using namespace std;



int main()

{

    // vector is a template, the <int> means it is a vector of ints

    vector<int> numbers;  



    // push_back() puts a new value at the end (or back) of the vector

    for (int i = 0; i < 10; i++)

        numbers.push_back(i);



    cout << "print all elements in vector" << endl;



    // This is one way to iterate through a vector and print all the values

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

        cout << numbers[i] << endl;



    // This is the preferred way to iterate through a vector



    // an iterator is a special object used to keep track of internal structures

    vector<int>::iterator iter;

    for (iter = numbers.begin(); iter != numbers.end(); iter++)

        cout << *iter << endl;



    cout << "now print it backwards" << endl;

    iter = numbers.end();

    for (iter--; iter != numbers.begin(); iter--)

        cout << *iter << endl;

    cout << *iter << endl;

}



// In order to motivate why the iterator mechanism show above is more 

// efficient that using the index method (the numbers[i] method)

// consider how you would implement finding a specific element of a 

// linked list.  Each time this function is called it has to start

// at the head of the list.



/*

bool List::index(int i, int &value)

{

    Node *ptr;

    for (ptr = m_head; i > 0; ptr = ptr->m_next, i--)

        ;

    if (ptr != NULL)

    {

        value = ptr->m_value;

        return true;

    }

    else return false;

}

*/