KwickClips Python · 40 sec · free
What is the base case for sum of digits?
Short answer. A single digit, n < 10.
How does recursion solve a problem?
Find the simplest case, then shrink the problem.
Base and recursive case
| Program | Base case | Recursive |
|---|---|---|
| factorial | n <= 1: 1 | n * f(n-1) |
| Fibonacci | n <= 1: n | f(n-1)+f(n-2) |
| digit sum | n < 10: n | n%10+f(n//10) |
Remember
| Find the simplest case first |
| Then shrink the problem |
Three classic recursions for tests. Here f is the function and n the number. Factorial stops at one. Fibonacci stops at n, else adds two terms. Digit sum stops at one digit. Find the simplest case. Then shrink the problem.
This clip is from the full lesson: Recursion in Python — 8 minutes, with the tables, the quick answers and the whole lesson in text.
Useful for: Programming All levels Python, Programming All levels C++
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