April 12

... start recording.

Last time I pointed you towards a lot of material on graphs, trees, how to get them into a computer, and how to search them.

Today we're going to be doing some coding work, practicing working with trees, graphs, and searching, in breakout rooms and all together. Please remind me to turn the recording on & off as we go.

I have some of my code in ../code/graphs ; we'll start from scratch and then look at some of that as needed.

vocabulary :

• tree : made up of nodes, each with children & parent
• graph : made up of vertices, each with neighbors, connected by edges
• search: visiting each node or vertex, doing something with each
• static: put everything into memory before searching
• dynamic: generate tree or graph elements as needed

API choices :

• put nodes or edges or something into a list or dictionary or whatever
• or wrap the whole Graph into an object with an API
• or put individual Node or Vertex or Edge components into objects
• or some combination

tasks :

• create image from graph edges using graphviz.org "dot" shell utility
• store graph as
  • collection of edges, or
  • neighbors of each vertex, or
  • matrix of vertex connections
• store tree as
  • children of nodes
• recursively search tree, using node children API
• breadth-first or depth-first search graph with "fringe" idea, using Stack, Queue, and vertex neighbors API

Here's what we'll start with :

We worked together through the attached tree_april12.py and graph_april12.py , which (a) store that graph into the code as a list of edges, (b) has a way to get children or neighbors, and (c) uses that to "search" through the whole tree or graph.

The homework for Thursday is basically these same tasks along with some explanations, on a different graph and tree.

I forgot to turn recording back on after our break, so the video only has the first part of today's class.

aside

• "existential sort"

attachments

		last modified	size
	graph_april12.py	Mon Apr 12 2021 05:34 pm	3.2K