title: Find common prefix of strings
body: <p>I am having 4 strings:</p>
  
  <pre><code>"h:/a/b/c"
  "h:/a/b/d"
  "h:/a/b/e"
  "h:/a/c"
  </code></pre>
  
  <p>I want to find the common prefix for those strings, i.e. <code>"h:/a"</code>.
  How to find that?</p>
  
  <p>Usually I'd split the string with delimiter <code>'/'</code> and put it in another list, and so on.<br>
  Is there any better way to do it?</p>