Add class 8 topics, resources, and challenges: sets and circular buffers

Author: neptunius

Class8.md

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+## Class 7: Sets & Circular Buffers
+
+### Topics
+- Abstract data types: [set], [multiset (bag)][multiset]
+- Concrete data structures: [hash table], [circular buffer (circular queue, ring buffer)][circular buffer]
+- [Set operations]
+
+### Challenges
+- Implement `Set` class (set with hash table) with the following [set operations] as instance methods and properties:
+    - `__init__(elements=None)` - initialize a new empty set structure, and add each element if a sequence is given
+    - `size` - property that tracks the number of elements in constant time
+    - `contains(element)` - return a boolean indicating whether `element` is in this set
+    - `add(element)` - add `element` to this set, if not present already
+    - `remove(element)` - remove `element` from this set, if present, or else raise `KeyError`
+    - `union(other_set)` - return a new set that is the union of this set and `other_set`
+    - `intersection(other_set)` - return a new set that is the intersection of this set and `other_set`
+    - `difference(other_set)` - return a new set that is the difference of this set and `other_set`
+    - `is_subset(other_set)` - return a boolean indicating whether `other_set` is a subset of this set
+- Write unit tests for to ensure the `Set` class is robust
+    - Include test cases for each class instance method
+- Annotate all instance methods with complexity analysis of running time and space (memory)
+- Compare the behaviors of your `Set` class to those of the [Python `set` type]
+
+### Stretch Challenges
+- Implement `CircularBuffer` class with dynamic array
+- Write unit tests for to ensure the `CircularBuffer` class is robust
+    - Include test cases for each class instance method
+- Annotate `enqueue` and `dequeue` methods with running time complexity analysis
+
+
+[set]: https://en.wikipedia.org/wiki/Set_(abstract_data_type)
+[multiset]: https://en.wikipedia.org/wiki/Set_(abstract_data_type)#Multiset
+[set operations]: https://en.wikipedia.org/wiki/Set_(abstract_data_type)#Operations
+[hash table]: https://en.wikipedia.org/wiki/Hash_table
+[circular buffer]: https://en.wikipedia.org/wiki/Circular_buffer
+[Python `set` type]: https://docs.python.org/3/library/stdtypes.html#set

ReadMe.md

@@ -16,7 +16,7 @@
 |   5   | Wednesday, November 1  | [Lists, Stacks & Queues](Class5.md)        |
 |   6   |    Friday, November 3  | [Call Routing Project](Class6.md)          |
 |   7   |    Monday, November 6  | [Maps & Hash Tables](Class7.md)            |
-|   8   | Wednesday, November 8  | Set & Circular Buffer         |
+|   8   | Wednesday, November 8  | [Sets & Circular Buffers](Class8.md)       |
 |   9   |    Friday, November 10 | Trees                         |
 |  10   |    Monday, November 13 | Tree Traversals               |
 |  11   | Wednesday, November 15 | Iterative Sorting Algorithms  |