madison metro data

tylerharter · Feb 9, 2020 · 6794818 · 6794818
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diff --git a/s20/lab4/README.md b/s20/lab4/README.md
@@ -2,7 +2,7 @@
 
 Start a new notebook on your virtual machine, then complete the two parts of the lab:
 
-1. learn about [linked lists](part1.md) -- this is good practice to prepare for the next topics in the course, trees and grahps
+1. learn about [linked lists](part1.md) -- this is good practice to prepare for the next topics in the course, trees and graphs
 2. learn about [zipped data](part2.md) -- for P2 (released after this lab), we'll ask you to analyzed data directly in a zip file, without unzipping first; you'll practice that here
 
 Have fun, and let us know if you have any questions!
diff --git a/s20/lab4/part1.md b/s20/lab4/part1.md
@@ -215,4 +215,15 @@ B occurs 2 times
 D occurs 1 times
 ```
 
-Pretty cool, huh?
+We get two useful methods, `.index(...)` and `.count(...)` by only
+adding one parent class.  Pretty cool, huh?
+
+## Concluding Thoughts
+
+Although we were able to implement something that works somewhat like
+a Python list, it wouldn't be a good idea to use our version as is.
+With a regular Python list, index lookups to the last items (like
+`L[-1]`) are fast -- they have O(1) complexity.  Although
+`__getitem__` doesn't use a loop, the recursion still need to go
+through every node to find the last one, so `L[-1]` is an `O(N)`
+operation for our version of the list -- ouch.
diff --git a/s20/p2/mmt_gtfs.zip b/s20/p2/mmt_gtfs.zip