Is there difference between two for form in C++?
<pre><code>vector&lt;int&gt; a;
</code></pre>

<p>1.</p>

<pre><code>for(vector&lt;int&gt;::iterator it = a.begin(); it != a.end(); ++it)
</code></pre>

<p>2.</p>

<pre><code>vector&lt;int&gt;::iterator end = a.end();
for(vector&lt;int&gt;::iterator it = a.begin(); it != end; ++it)
</code></pre>

<p>which is more efficient？or the same?</p>
