alexcarrizo / Factorial-Playground

Swift playground for calculating the factorial of an integer n by iteration or recursion, with execution time

Factorial Playground

Swift playground for calculating the factorial of an integer n by iteration or recursion, with execution time.

Factorial Definition

"In mathematics, the factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n. For example,

5! = 5 x 4 x 3 x 2 x 1 = 120." - from https://en.wikipedia.org/wiki/Factorial

How to use

Set n to the integer of your choice, then set the algorithm type

let n = 5
let solveBy: AlgorithmType = .recursion

Click here to view source

Playground Notes

• By definition, 0! = 1
• Handles negative integers, just know that -20! is actually -(20!)
• Works with integers from -20 to 20

My results

Testing recursion

20! = 2432902008176640000

Time elapsed for getFactorialByRecursion(20): 810.027122497559 ns

Testing iteration

20! = 2432902008176640000

Time elapsed for getFactorialByIteration(20): 833.988189697266 ns

After repeated testing, it appears that recursion is slightly faster than iteration when calculating factorials using these methods.