Likes
=====

Consider a scenario of a social network where people "gives *likes*" to each other. Let's use an example represented in the follwing picture where nodes are people and directed arrows represent that the origin gave a like to the target:


    .. image:: likes.jpeg
        :width: 800px
        :height: 400px
        :scale: 50 %
        :alt: alternate text
        :align: center


The information about the "likes" can be represented in Python as a dictionary where the keys are person names in the network (:class:`str`) and the associated value is the list of people names (:class:`list` of :class:`str`) to whom that person gave a like.

For example:

    .. literalinclude:: compute_likedby_dict.test
        :language: pycon
        :start-after: --ini-in
        :end-before: --fi-in

.. note:: We assume that all likes involve people appearing as a key in the dictionary (no likes to people who is not in the network.


You are required to implement the following functions and deliver them in the module :mod:`likes` (file :file:`likes.py`).


------------------------------------------------------------------------------------------------

The first function is:

    .. py:function:: compute_likedby_dict(likesD)

such that

    **given** *likesD* (:class:`dict`) a *likes dictionary* as described above.
    **returns** a new :class:`dict` where:

        #. The keys are all the names (:class:`str`) of people in the network.
        #. The value associated to each key is a :class:`list` with all the names of people that has given a like to the key person. The names must be **alphabetically ordered**.

    The input :class:`dict` should **not** be modified.

.. note::

    The new dict must also include the people who did not receive any like, whose value will consequently be the empty list.

For example, the expected outpout for the above *likes* :class:`dict` would be:

    .. literalinclude:: compute_likedby_dict.test
        :language: pycon
        :start-after: --ini-out
        :end-before: --fi-out

Doctests are available in the :download:`compute_likedby_dict.test` file.


------------------------------------------------------------------------------------------------

The second function is:

    .. py:function:: compute_matches_list(langD)

such that

    **given** *likesD* (:class:`dict`) a *likes dictionary* as described above.

    **returns** a :class:`list` of pairs of people (:class:`tuple`) that **matched**. Both, the names inside each tuple and the list of tuples must be **alphabetically ordered**.

For example, the expected outpout for the above example dict would be:

    .. literalinclude:: compute_matches_list.test
        :language: pycon
        :start-after: --ini-out
        :end-before: --fi-out

Doctests are available in the :download:`compute_matches_list.test` file.