KwickClips Java · 45 sec · free
What is the base case of GCD?
Short answer. When b becomes 0, the answer is a.
Why is recursive Fibonacci slow?
Each call makes two more calls.
Base and recursive
| Program | Base | Recursive |
|---|---|---|
| fact(n) | n<=1: 1 | n*fact(n-1) |
| fib(n) | n<=1: n | f(n-1)+f(n-2) |
| gcd(a,b) | b==0: a | gcd(b,a%b) |
| pow(b,e) | e==0: 1 | b*pow(b,e-1) |
Remember
| Find the base case first |
| Then shrink the input |
Four recursion programs exams love. Know them? Here are all four. Factorial stops at one. Fibonacci, f here, adds two calls. GCD stops when b is zero. Power stops at exponent zero. Remember. Find the base case. Then shrink the input.
This clip is from the full lesson: Recursion in Java — 8 minutes, with the tables, the quick answers and the whole lesson in text.
Useful for: ISC Class 11 Computer Science (868), ISC Class 12 Computer Science (868), ISC Class 12 Computer Science (868), Programming All levels Java
More KwickClips from this lesson
Where do waiting calls go?44 sec
Why does my recursion crash with StackOverflowError?41 sec
Can you reverse a word without a loop?41 secDisclaimer. KwickAcademy is free study material for general learning and revision. Parts of it, including the voice-over, are produced with the help of AI tools and may contain errors; if you spot one, please tell us and we will correct it. Syllabus, marks and exam details follow the latest official board publications available to us, and boards can change them at any time, so always confirm against your board's official website and your school. Using this material does not guarantee any marks or result. Board names and trademarks belong to their owners; Kwickprep is not affiliated with or endorsed by any examination board. We never ask for passwords, OTPs or ID numbers. Your progress is saved only in this browser. Full disclaimer · Privacy