title: Ruby - extracting the unique values per key from an array of hashes
body: <p>From a hash like the below one, need to extract the unique values per key</p>
  
  <pre><code>array_of_hashes = [ {'a' =&gt; 1, 'b' =&gt; 2 , 'c' =&gt; 3} , 
                      {'a' =&gt; 4, 'b' =&gt; 5 , 'c' =&gt; 3}, 
                      {'a' =&gt; 6, 'b' =&gt; 5 , 'c' =&gt; 3} ]
  </code></pre>
  
  <p>Need to extract the unique values per key in an array</p>
  
  <p>unique values for 'a' should give</p>
  
  <pre><code>[1,4,6]
  </code></pre>
  
  <p>unique values for 'b' should give</p>
  
  <pre><code>[2,5]
  </code></pre>
  
  <p>unique values for 'c' should give</p>
  
  <pre><code>[3]
  </code></pre>
  
  <p>Thoughts ? </p>