title: Run length encoding using O(1) space
body: <p>Can we do the run-length encoding in place(assuming the input array is very large)
  We can do for the cases such as AAAABBBBCCCCDDDD
  A4B4C4D4</p>
  
  <p>But how to do it for the case such as ABCDEFG?
  where the output would be A1B1C1D1E1F1G1</p>