<div dir="ltr">There is a problem in student class. Right now the less than function is as following:<br>   friend bool operator&lt; (Student left, Student right){<br>      return left.lastName_ &lt; right.lastName_ ||<br>         (left.lastName_ == right.lastName_ &amp;&amp;<br>          left.firstName_ &lt; left.<b>lastName_</b>);<br>   }<br><br>It should be:<br><br>   friend bool operator&lt; (Student left, Student right){<br>      return left.lastName_ &lt; right.lastName_ ||<br>         (left.lastName_ == right.lastName_ &amp;&amp;<br>          left.firstName_ &lt; left.<b>firstName_</b>);<br><div>   }</div><div><br></div><div>Thanks</div><div>Tamim<br></div></div>