# https://classroom.udacity.com/nanodegrees/nd256/parts/b835ca8d-4269-4ca3-b911-c8ceb9cc0aa0/modules/a5f68248-862f-4a72-8682-24b86e2f6d61/lessons/a640374a-90af-40ad-85ff-1c6ce3948219/concepts/d4a73c15-f614-4674-80f4-2449ef50abc4

class LRU_Cache(object):

    def __init__(self, capacity):
        # Initialize class variables
        pass

    def get(self, key):
        # Retrieve item from provided key. Return -1 if nonexistent. 
        pass

    def set(self, key, value):
        # Set the value if the key is not present in the cache. If the cache is at capacity remove the oldest item. 
        pass

our_cache = LRU_Cache(5)

our_cache.set(1, 1);
our_cache.set(2, 2);
our_cache.set(3, 3);
our_cache.set(4, 4);


our_cache.get(1)       # returns 1
our_cache.get(2)       # returns 2
our_cache.get(9)      # returns -1 because 9 is not present in the cache

our_cache.set(5, 5) 
our_cache.set(6, 6)

our_cache.get(3)      # returns -1 because the cache reached it's capacity and 3 was the least recently used entry
