Run-length Encoding |2|
~~~~~~~~~~~~~~~~~~~~~~~

Run-length encoding is a fast and simple method of encoding strings. The
basic idea is to represent repeated successive characters as a single
count and the character. For example, the ``string`` “AAAABBBCCDAA”
would be encoded as “4A3B2C1D2A”.

Write a program to run-length encode a given string and print the
result. The input string will have no digits and has only uppercase
alphabetic characters.

.. container:: sampleio

   Sample I/O:

.. |2| image:: ../../figures/difficulty_four.png
   :class: difficulty

.. code:: default

   Input:
   AAAABBBCCDAA

   Output:
   4A3B2C1D2A

   Input:
   AABBA

   Output:
   2A2B1A

.. raw:: html

   <button type="button" class="collapsible" onclick="toggle()">

Show the Answer

.. raw:: html

   </button>

.. raw:: html

   <div class="hiddenanswer">

.. code:: python

   s = input()

   cursor = ""       # to keep the current character
   streak = 1
   buildup = ""
   for a in s:
       if a != cursor:
           if cursor != "":
               buildup += str(streak) + cursor     # notice the casting int to string
           cursor = a
           streak = 1
       else:
           streak += 1
   buildup += str(streak) + cursor

   print(buildup)

.. raw:: html

   </div>