Traversing a 2D array

Sample lesson 3. Every activity works the way it does in class, but nothing counts: no real claim code is made and no form opens. Start with the first one: each activity has a Next button at the bottom, and Overview brings you back here.

The big idea. A 2D array is a grid of rows, and a traversal is a nested loop that visits the cells: row-major goes across each row, column-major goes down each column, and a partial traversal visits one row, one column, or the border.

1. 1Do Now
   The first 10 minutes. Spot the trap: a few quick questions on the last lesson, and a wrong answer shows why.
2. 2Textbook
   What we are learning to do today, the explanation with diagrams, then a worked problem one step per click. Click or use the arrow keys.
3. 3Scrum pod
   One challenge in steps, worked at the table: each step opens when the one before is right.
4. 4We Do / You Do
   The follow-along jobs from the Textbook, then Part A with help, Part B like the exam, and a stretch.
5. 5Exit ticket
   A tiny AP exam: each question is answered once, with no feedback until every one is in.