title: Iterating over a two dimensional array in Ruby
body: <p>Just need a little bit of help iterating over a 2-dimensional array in Ruby. </p>
  
  <p>If I have the following 2-d array:</p>
  
  <pre><code>a = [[1,2,3], 
       [4,5,6], 
       [7,8,9]]
  </code></pre>
  
  <p>Say [1,2,3] across are 'rows' and [1,4,7] down are 'columns'. </p>
  
  <p>Say I have another array:</p>
  
  <pre><code>b = [3,6,9]
  </code></pre>
  
  <p>How can I iterate over a to see if [3,6,9] is a column in a?</p>