title: Count the number of unique characters in a string using only for loops and if/else operations
body: <p>I am supposed to find the number of unique characters in a string.</p>
  <p>Here's the catch, no arrays or even <code>while</code> loops (although <code>for</code> loop can accomplish this). I can't seem to do it without writing a bunch of ridiculous <code>if</code>-<code>else</code> statements under a <code>for</code> loop checking each char value against each other.</p>