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More Recursion!

We continue our discussion on recursion. Here are the slides for all 3 videos of this lecture: pdf. The answers to the questions asked during this lecture are in a separate file at the end of this page.

Part 1: Call stack

We focus on what happens in memory when we execute a recursive function: the call stack grows with each recursive call, until a base case is reached and the call returns. All the calls eventually wrap up, accumulating the final result.

• video
• audio only
• Code: factorial.py is the same as that posted for Lecture 17

Part 2: More ways to divide (and conquer)

There are different ways to break up the problem into parts, but you need to make sure that each part will progress to the base case eventually and that the answers from the parts are combined correctly.

• video
• audio only
• Code: stringExamples.py

Part 3: Recursion and objects

Given a "family tree" represented using a Person objects, we write a function to determine the number of ancestors that a person has.

• video
• audio only
• No code file is provided. The next topic in the course is "defining classes" and you'll learn about how to define a class such as Person then.
• The final question given in this lecture is optional--perhaps work on it after you complete your lab exercise this week?

Answers to the first 4 questions asked during lecture: pdf