title: time complexity for comparing two strings
body: <p>How is the running time of the ff function <code>o(nlogn)</code>?</p>
  
  <pre><code>function isPermutation(a, b) {
      if (a.length !== b.length) {
          return false;
      }
      return a.split("").sort().join() === b.split("").sort().join();
  }
  </code></pre>
  
  <p>aren't you checking the length of both strings, or is it dependent on the implementation of sort?</p>