title: Design a datastructure for telephone directory
body: <p>Design a datastructure for telephone directory for storing the name and phone number so that we can search for key given name and vice versa.</p>
  
  <p>We can use 2 hash maps as follows</p>
  
  <pre><code>Map&lt;String,int&gt;
  Map&lt;int,String&gt;
  </code></pre>
  
  <p>But it requires twice the memory.Can anyone suggest any other solution?</p>