Add notes on the topic

notes-and-examples/2026.08.27/overview.md

@@ -0,0 +1,5 @@
+## Overview
+
+We'll go over exercise 2 from [last week](../2026.08.20/overview.md), as well as
+a new topic: [topological sort](./topological_sort.md). Try to complete the 
+exercise from the document.

notes-and-examples/2026.08.27/topological_sort.md

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+## Class ordering
+
+These are some classes for Chapman University, for
+the [computer science program](https://catalog.chapman.edu/preview_program.php?catoid=33&poid=6408&print).
+
+![An ordering of classes for Chapman University.](classes.png)
+
+> [!QUESTION] What type of graph is this?
+
+We say that a class is a *prerequisite* or a *dependency* of another class
+if we need to take it before that other class. So, we need to take CPSC 230
+before CPSC 231, for example.
+
+Could you come up with something like this for your school?
+
+## The algorithm
+
+If you were to come up with a list of classes, such that the list of classes
+is in the order which you need to take them, what would that look like?
+
+This order is what we're trying to achieve with the topological sort
+algorithm. Note that there can be multiple correct solutions.
+
+## The exercise
+
+Let's write the algorithm. First, test it against the Chapman classes, then
+put in your classes and see how it fares against that.

notes-and-examples/2026.08.27/topological_sort.py

@@ -15,7 +15,7 @@ classes = {
 }
 
 def topological_sort(adjacency_list: dict[str, set[str]]):
-    # return the sorted ordering
+    # return the sorted ordering ['CPSC 230', 'ENGR 101', 'CPSC 231', ...]
     return []
 
 print(topological_sort(classes))