1. Recursion
1. The computer science equivalent of mathematical induction.
2. A way of defining something in terms of itself.
3. Ex. f(n) = 1, if n ==1
f(n) = n + f(n - 1), if n > 1
=10
4. Ex. f(4) = 4 + f(3)
= 6
f(3) = 3 + f(2)
f(2) = 2 + f(1)
= 3
f(1) = 1
f(4) =

2. 7. Can we get the same output without recursion?
6. Note: this example of a recursive function is an arithmetic series. Σi = 1 i = (1 + n)n/2 n
Ex. n = = (1 + 6)(6/2)
7. Can we get the same output without recursion?
8. Yes. Always. Using loops.
9. Rewrite WhatItDo() without recursion.
10. Recursion shortens code but may take a great deal more computer time and space, sometimes causing “stack overflow”. Therefore, only use recursion when it helps solve a problem.