Introduction to C++ STL vector

<pre><code><font color="#000000">
<font color="#008000">// on linux, compile with g++, or use the -lstdc++ switch on gcc</font>
<font color="#008000">#include <iostream> // for cout</font>
<font color="#008000">#include <vector> // for vector</font>
<font color="#0000ff">using namespace</font> std;
<font color="#0000ff">int</font> main(<font color="#0000ff">void</font>)
{
 <font color="#008000">// a vector is very similar to a standard C array</font>
 <font color="#008000">// one key difference is that a vector has dynamic size</font>
 <font color="#008000">// this means that you can add and delete items from it in a very simple fashion</font>
 <font color="#008000">// as you work with the vector, it handles all of the necessary memory management for you</font>
 <font color="#008000">// this allows you to focus on the more important parts of your programming task</font>
 <font color="#008000">//</font>
 <font color="#008000">//</font>
 <font color="#008000">// here are some of the various useful member functions of a vector:</font>
 <font color="#008000">//</font>
 <font color="#008000">// push_back() - adds an item to the end of the vector</font>
 <font color="#008000">// insert() - adds an item (or range of items) at a specified spot in the vector</font>
 <font color="#008000">// pop_back() - removes the item at the end of the vector</font>
 <font color="#008000">// erase() - removes the item (or range of items) at a specified spot in the vector</font>
 <font color="#008000">// size() - tells how many items are currently stored in the vector</font>
 <font color="#008000">// clear() - clears all items currently stored in the vector</font>
 <font color="#008000">// operator [] - the familiar brackets, used in the same manner as with standard C arrays, to access items</font>
 <font color="#008000">// create a vector container object - it will store ints in this example</font>
 <font color="#008000">// however, a vector can store almost any type of object</font>
 <font color="#008000">// from int and char, to string and custom classes, even other vectors (for a multi-dimensional vector)!</font>
 vector<<font color="#0000ff">int</font>> IntVector;
 <font color="#008000">// add an integer (value 24) to the end of the vector</font>
 IntVector.push_back(<font color="#0000ff">24</font>);
 <font color="#008000">// print out the current number of ints contained inside our vector</font>
 cout << <font color="#800000">"After push_backing one item, the vector's size is: "</font> << IntVector.size() << endl;
 <font color="#008000">// remove the element at the end of the vector</font>
 IntVector.pop_back();
 <font color="#008000">// print out the current number of ints contained inside our vector</font>
 cout << <font color="#800000">"After pop_backing one item, the vector's size is: "</font> << IntVector.size() << endl;
 cout << endl;
 <font color="#008000">// a variable we will use with our for loops</font>
 <font color="#0000ff">unsigned short</font> counter = <font color="#0000ff">0</font>;
 <font color="#008000">// let's add 10 items to the vector, inserting each at the beginning of the vector, instead of the end</font>
 <font color="#008000">// the first item we will add is 0, the final item we will add is 9</font>
 <font color="#0000ff">for</font>(counter = <font color="#0000ff">0</font> ; counter < <font color="#0000ff">10</font> ; counter++)
 {
  <font color="#008000">// the first parameter, IntVector.begin(), indicates to add the new item at the very beginning of the vector</font>
  <font color="#008000">// the second parameter, counter, indicates the variable (value) we wish to add to the vector</font>
  IntVector.insert( IntVector.begin(), counter);
 }
 <font color="#008000">// print out the current number of ints contained inside our vector</font>
 cout << <font color="#800000">"After inserting 10 items, the vector's size is: "</font> << IntVector.size() << endl;
 <font color="#008000">// print out the vector's current contents, item by item</font>
 <font color="#008000">// we will start with item 0 (like a standard C array)</font>
 <font color="#008000">// we will want to stop at item 9 (like a standard C array)</font>
 <font color="#008000">// notice the output starts at 9 and decreases from there</font>
 <font color="#008000">// this is because we added the items in our previous loop to the beginning of the vector, and not to the end</font>
 <font color="#0000ff">for</font>(counter = <font color="#0000ff">0</font> ; counter < IntVector.size() ; counter++)
 {
  <font color="#008000">// we use IntVector[counter] to access an item's value, just like a standard C array</font>
  cout << <font color="#800000">"Item "</font> << counter << <font color="#800000">" contains: "</font> << IntVector[counter] << endl;
 }
 cout << endl;
 <font color="#008000">// let's erase item 6</font>
 <font color="#008000">// we only pass one parameter to erase, since we are deleting only one item</font>
 <font color="#008000">// this parameter indicates which item to delete</font>
 IntVector.erase( IntVector.begin() + <font color="#0000ff">6</font> );
 <font color="#008000">// print out the current number of ints contained inside our vector</font>
 cout << <font color="#800000">"After erasing one item, the vector's size is: "</font> << IntVector.size() << endl;
 <font color="#008000">// let's erase items 0-3. note: that is 4 items to be deleted</font>
 <font color="#008000">// we pass two parameters this time, the first indicates the item position to begin erasing at</font>
 <font color="#008000">// the second parameter indicates the item position to stop deleting at (this item does not get erased)</font>
 IntVector.erase( IntVector.begin(), IntVector.begin() + <font color="#0000ff">4</font> );
 <font color="#008000">// print out the current number of ints contained inside our vector</font>
 cout << <font color="#800000">"After erasing four more items, the vector's size is: "</font> << IntVector.size() << endl;
 <font color="#008000">// print out the current vector contents</font>
 <font color="#0000ff">for</font>(counter = <font color="#0000ff">0</font> ; counter < IntVector.size() ; counter++)
 {
  <font color="#008000">// we use IntVector[counter] to access an item's value, just like a standard C array</font>
  cout << <font color="#800000">"Item "</font> << counter << <font color="#800000">" contains: "</font> << IntVector[counter] << endl;
 }
 <font color="#008000">// clear the vector</font>
 <font color="#008000">// note: it is not necessary to clear the vector when you are finished using it</font>
 <font color="#008000">// all memory deallocation is handled automatically</font>
 <font color="#008000">// </font>
 <font color="#008000">// it is only necessary when you want to erase everything inside of it and start out fresh</font>
 IntVector.clear();
 <font color="#008000">// print out the current number of ints contained inside our vector</font>
 cout << <font color="#800000">"After clearing the vector, the vector's size is: "</font> << IntVector.size() << endl;
 <font color="#0000ff">return 1</font>;
}
</font>
</code></pre>