title: jquery multiple dropdownlist validation
body: <p>I have n number of dropdownlists with the same options and values. </p>
  
  <p>I want to validate it, that only the unique value could be selected among these n dropdownlists. n is random number. </p>
  
  <p>Example:</p>
  
  <p>I have 3 ddl with these values:</p>
  
  <pre><code>&lt;select&gt;
  &lt;option value="apple" selected="yes"&gt; Apple &lt;/option&gt;
  &lt;option value="carrots"&gt; Carrots &lt;/option&gt;
  &lt;option value="potatoes"&gt; Potatoes &lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>and I want to have unique selected values for each dropdownlist, so if you select apples and try to select apples again on another ddl, it changes a previous one to the available value or prompts an alert..</p>