title: Reverse words of a sentence
body: <p>I want to reverse a sentence. For example, my string is like follows.</p>
  
  <pre><code> str = "I am a good boy"
  </code></pre>
  
  <p>I want the result <code>"boy good a am I"</code>. I can reverse the string by using built in Ruby methods like:</p>
  
  <pre><code> str.split(" ").reverse.join(" ") #=&gt; "boy good a am I"
  </code></pre>
  
  <p>Is there any way to do this without using Ruby built in methods?</p>