Shoe shop
===========

The supplies of a shoe shop are represented by a list of articles
corresponding to shoe sizes. An article is represented with a list of
two integers that stand for, respectively, the size and the number of
pairs of shoes of this size stored in the shoe shop. The list of
articles is not ordered according to any criteria and each size only
appears once.

#. Write the function :py:func:`shoeshop1` that from a list of
   articles and two integers corresponding to two sizes, ``s1`` and
   ``s2``, returns that size between ``s1`` and ``s2`` (both included)
   with the maximum number of pairs of shoes. If there were more than
   one size fulfilling these requirements, the first one encountered
   must be returned. If there is any size fulfilling these
   requirements, or the given list is empty, the function will return
   -1. Save this function into the file ``shoeshop1.py``. Examples:
   
   .. literalinclude:: test-shoeshop1.txt
      :language: python3
      :lines: 3-

   .. note::

      More tests are provided in file :download:`test-shoeshop1.txt <test-shoeshop1.txt>`
	  
   .. rubric:: Solution

   A solution of this function is provided in the :download:`shoeshop1.py <solutions/shoeshop1.py>`

#. Save this function as well as the next ones into the same file
   ``shoeshop2.py``. Write the function :py:func:`search_size` that
   from a list of articles and an integer indicating a size, returns
   the position in the list of articles of the article corresponding
   to that size. If the size does not appear in the list of articles,
   this function must return -1. Examples:
   
   .. literalinclude:: test-shoeshop2.txt
      :language: python3
      :lines: 3-
   .. note::
      More tests are provided in file :download:`test-shoeshop2.txt <test-shoeshop2.txt>`


#. Write the **modifier** function :py:func:`update_size` that from a list
   of articles, an integer indicating the position of an article and
   another integer indicating a number of pairs of shoes, updates the
   list by increasing the units of the article corresponding to the
   given position with the given amount of pairs of shoes. Examples:
   
   .. literalinclude:: test-shoeshop3.txt
      :language: python3
      :lines: 3-

   .. note::
      More tests are provided in file :download:`test-shoeshop3.txt <test-shoeshop3.txt>`

	    
#. Write the **modifier** function :py:func:`update_stock` that given
   a list of items corresponding to the supplies of the shoe shop and
   another list of articles corresponding to new pairs of shoes
   entering to the shop, updates the first list with the entries in
   the second list. This function must call the previous two
   functions. Examples:
   
   .. literalinclude:: test-shoeshop4.txt
      :language: python3
      :lines: 3-

   .. note::
      More tests are provided in file :download:`test-shoeshop4.txt <test-shoeshop4.txt>`

	  
   .. rubric:: Solution
	    
   A solution of this function and the two previous ones  is provided in file :download:`shoeshop2.py <solutions/shoeshop2.py>`