title: How to 'zero' out rows & columns in an array
body: <p>I have a 2D array to represent a many-many mapping :</p>
  
  <pre><code>0   3   1   3
  3   0   0   0
  1   0   0   0
  3   0   0   0
  </code></pre>
  
  <p>What is the quickest way to 'zero' out rows and column entries corresponding to a particular index in this array?</p>