AQA 7517 4.1.1.16: Recursive techniques
The free BugBot lessons that teach this point, a robot to try it on, and the past-paper questions that test it.
What it covers
At GCSE, merge sort (F5.9) sorted each half of a list "the same way", with a function that called itself. That idea is recursion: a subroutine that solves a problem by calling itself on a smaller version of the same problem. This lesson is about how to write recursion correctly, and how the call stack from the last lesson makes it work.
- Base case and general case
- Winding and unwinding
- What goes wrong
- Recursion on the robot
Or do it in the simulator, with tasks that mark themselves
Lessons that teach it
- A2.2 Recursion Recursion and computational thinking
Base case and general case, winding and unwinding, and a spiral the robot draws by calling itself. - A2.3 Recursion versus iteration Recursion and computational thinking
The same algorithm both ways, the cost of a frame per call, repeated work, and stack overflow. - A2.10 Project: out of the dead end Recursion and computational thinking
Model a maze, solve it by recursive backtracking, and drive the robot out along the route.
Try it on a robot
The task from A2.2 Recursion, running here. Change the program and press Run.
The specification is AQA's own document; this page says which of our lessons teach point 4.1.1.16 and is not endorsed by the board.