title: Add the least amount of characters to make a palindrome
body: <p>The question:</p>
  
  <blockquote>
    <p>Given any string, add the least amount of characters possible to make it a palindrome in linear time.</p>
  </blockquote>
  
  <p>I'm only able to come up with a O(N<sup>2</sup>) solution.</p>
  
  <p>Can someone help me with an O(N) solution?</p>