How to create new string in C++ by two other ones? : <p>I want to create <code>string</code> <code>"hello1world</code> by this two strings:</p>

<pre><code>string s1 = "hello"
string s2 = "world" 
</code></pre>

<p>I do this:</p>

<pre><code>string my_str;
sprintf(my_str, "%s1%s", s1, s2);
</code></pre>

<p>But I have an error:</p>

<pre><code>error: cannot convert ‘std::__cxx11::string {aka std::__cxx11::basic_string&lt;char&gt;}’ to ‘char*’ for argument ‘1’ to ‘int sprintf(char*, const char*, ...)’
     sprintf(my_str, "%s1%s", s1, s2);
</code></pre>

<p>How to do it properly?</p>
