C++ Remove all non-number charachters from std::string : <p>What is an efficient way to remove all chars within in a string which are not in the range from 0 to 9?</p>

<pre><code>string s = "h3ll0";
string numbers = removeNonNumbersFromString(s);
cout &lt;&lt; numbers &lt;&lt; endl;
</code></pre>

<p>output should be <code>30</code></p>
