title: Number of Subarray whose sum greater than given value
body: <p>Given an array of <em>N</em> integers (positive and negative), find the number of <strong>contiguous</strong> sub array whose sum is greater or equal to <em>K (also, positive or negative)</em></p>
  
  <p>I have managed to work out a naive O(N<sup>2</sup>) solution, is it possible to get better?</p>