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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head>  <meta name="generator" content=  "HTML Tidy for Linux/x86 (vers 1 September 2005), see www.w3.org">  <title>C++ Iterators</title>  <link href="cppreference.css" rel="stylesheet" type="text/css"></head><body><table>  <tr>  <td>  <div class="body-content">  <div class="header-box">    <a href="index.html">cppreference.com</a> &gt; C++ Iterators  </div>  <h3>C++ Iterators</h3>  <p>Iterators are used to access members of the container classes, and  can be used in a similar manner to pointers. For example, one might  use an iterator to step through the elements of a <a href=  "cppvector/index.html">vector</a>. There are several different types  of iterators:</p>  <table class="misc-table">    <tr class="misc-table-tr-1">      <th>Iterator</th>      <th>Description</th>    </tr>    <tr class="misc-table-tr-2">      <td>input_iterator</td>      <td>Read values with forward movement. These can be incremented,      compared, and dereferenced.</td>    </tr>    <tr class="misc-table-tr-1">      <td>output_iterator</td>      <td>Write values with forward movement. These can be incremented      and dereferenced.</td>    </tr>    <tr class="misc-table-tr-2">      <td>forward_iterator</td>      <td>Read or write values with forward movement. These combine the      functionality of input and output iterators with the ability to      store the iterators value.</td>    </tr>    <tr class="misc-table-tr-1">      <td>bidirectional_iterator</td>      <td>Read and write values with forward and backward movement.      These are like the forward iterators, but you can increment and      decrement them.</td>    </tr>    <tr class="misc-table-tr-2">      <td>random_iterator</td>      <td>Read and write values with random access. These are the most      powerful iterators, combining the functionality of bidirectional      iterators with the ability to do pointer arithmetic and pointer      comparisons.</td>    </tr>    <tr class="misc-table-tr-1">      <td>reverse_iterator</td>      <td>Either a random iterator or a bidirectional iterator that      moves in reverse direction.</td>    </tr>  </table>  <p>Each of the container classes is associated with a type of  iterator, and each of the STL algorithms uses a certain type of  iterator. For example, vectors are associated with  <strong>random-access iterators</strong>, which means that they can  use algorithms that require random access. Since random-access  iterators encompass all of the characteristics of the other  iterators, vectors can use algorithms designed for other iterators as  well.</p>  <p>The following code creates and uses an iterator with a vector:</p>  <pre>  vector&lt;int&gt; the_vector;  vector&lt;int&gt;::iterator the_iterator;  for( int i=0; i &lt; 10; i++ )    the_vector.push_back(i);  int total = 0;  the_iterator = the_vector.begin();  while( the_iterator != the_vector.end() ) {    total += *the_iterator;    the_iterator++;  }  cout &lt;&lt; &quot;Total=&quot; &lt;&lt; total &lt;&lt; endl;</pre>Notice that you can access the elements of the container bydereferencing the iterator.  </div>  </td>    </tr>  </table></body></html>
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