title: Minimal number of covering boxes for binary matrix
body: <p>I have a binary matrix n*m (0's and 1's). Problem is to cover all 1's with non-overlapping boxes whose elements are all 1.</p>
  
  <p>Example:</p>
  
  <pre><code>1111
  0110
  0110
  </code></pre>
  
  <p>Box can be represent with coordinates and lengths in each coordinate <code>(x,y,lx,ly)</code>. This example is covered with 2 boxes <code>{ (0,0,1,4), (1,1,2,2) }</code>.</p>
  
  <p>I'm looking how to find cover with minimal number of boxes.</p>
  
  <p>Thanks</p>