H e r b S c h i l d t ' s C + + P r o g r a m m i n g C o o k b o o k The following example shows vector in action:

The following example shows vector in action:
// Demonstrate vector.
#include <iostream>
#include <vector>
using namespace std;
void show(const char *msg, vector<int> vect);
int main() {
// Declare a vector that has an initial capacity of 10.
vector<int> v(10);
// Assign its elements some values. Notice how this is
// done using the standard array-subscripting syntax.
// Notice that the number of elements in the vector is
// obtained by calling size().
for(unsigned i=0; i < v.size(); ++i) v[i] = i*i;
show("Contents of v: ", v);
// Compute the average of the values. Again, notice
// the use of the subscripting operator.
int sum = 0;
for(unsigned i=0; i < v.size(); ++i) sum += v[i];
double avg = sum / v.size();
cout << "The average of the elements is " << avg << "\n\n";
// Add elements to the end of v.
v.push_back(100);
v.push_back(121);
show("v after pushing elements onto the end: ", v);
cout << endl;
// Now use pop_back() to remove one element.
v.pop_back();
show("v after back-popping one element: ", v);
cout << endl;
cout << "The first and last element in v as"
<< " pointed to by begin() and end()-1:\n"
<< *v.begin() << ", " << *(v.end()-1) << "\n\n";
cout << "The first and last element in v as"
<< " pointed to by rbegin() and rend()-1:\n"
<< *v.rbegin() << ", " << *(v.rend()-1) << "\n\n";
// Declare an iterator to a vector<int>.
vector<int>::iterator itr;

// Now, declare reverse iterator to a vector<int>
vector<int>::reverse_iterator ritr;
// Cycle through v in the forward direction using an iterator.
cout << "Cycle through the vector in the forward direction:\n";
for(itr = v.begin(); itr != v.end(); ++itr)
cout << *itr << " ";
cout << "\n\n";
cout << "Now, use a reverse iterator to cycle through in the"
<< " reverse direction:\n";
// Cycle through v in the reverse direction using a reverse_iterator.
for(ritr = v.rbegin(); ritr != v.rend(); ++ritr)
cout << *ritr << " ";
cout << "\n\n";
// Create another vector that contains a subrange of v.
vector<int> v2(v.begin()+2, v.end()-4);
// Display the contents of v2 by using an iterator.
show("v2 contains a subrange of v: ", v2);
cout << endl;
// Change the values of some of v2's elements.
v2[1] = 100;
v2[2] = 88;
v2[4] = 99;
show("After the assignments, v2 now contains: ", v2);
cout << endl;
// Create an empty vector and then assign it a sequence
// that is the reverse of v.
vector<int> v3;
v3.assign(v.rbegin(), v.rend());
show("v3 contains the reverse of v: ", v3);
cout << endl;
// Show the size and capacity of v.
cout << "Size of v is " << v.size() << ". The capacity is "
<< v.capacity() << ".\n";
// Now, resize v.
v.resize(20);
cout << "After calling resize(20), the size of v is "
<< v.size() << " and the capacity is "
<< v.capacity() << ".\n";
// Now, reserve space for 50 elements.
v.reserve(50);
cout << "After calling reserve(50), the size of v is "
<< v.size() << " and the capacity is "
<< v.capacity() << ".\n";
return 0;
}

// Display the contents of a vector<int>.
void show(const char *msg, vector<int> vect) {
cout << msg;
for(unsigned i=0; i < vect.size(); ++i)
cout << vect[i] << " ";
cout << "\n";
}