Swift Fun Algorithms #3: Factorials & Recursion

Today's algorithm will be the relatively simple function known as the Factorial. I'm sure most of you guys know how a factorial works already. Thus lets go ahead and implement a simple for loop style factorial function. We will then move on to implementing the code using recursion! Trust me its a lot of fun.

Source code:

[nathanjeong]

only 2000 view?? come on guys study your Swift Fun Algorithms!! This video is worth millions of views

[kryptoshi]

Really nice and informative series Brain specially for some one interested in diving into competitive programming using swift, please do more of these.

[danieledstrom]

I really love recursion. It can be a real brain tease but when you get it to work it's almost like watching magic happen. Really powerfull stuff.

[cinquain]

LOL@ his comment at the end. « Recursions take a little bit of thought »

[story]

A more clear way to explain is
value * recursive(value - 1)
If value =3 then

3 * (3-1) * (2-1) * 1
If value = 4 then
4 * (4-1) * (3-1) * (2-1) * 1

[МахмуджанНиязов]

Спасибо браток выручил, от меня подписка и лайк)))

[hasanalisiseci]

What should I do if I want to find the factorial of a large number like 25?

[neeleshshah]

ternary op will shorten it further ..

func factorial(of num : Int) -> Int! {
return num < 0 ? nil : num == 0 ? 1 : num * factorial(of: num - 1)
}

[damiandudycz]

I would try:
func factorial(of value: Int) -> Int {
(1...value).reduce(1, *)
}
Should work right? :)
I know it's not what this video is about, but it seems nicer

[formulaint]

error: Recursions.playground:15:46: error: missing argument label 'value:' in call
return value * - 1) This doesn't seem to be working :(

[andreychirkov]

Great! Thanks! Really love this series! Very very interesting.

[GillesVandenPeereboom]

Hello Brian,
Excellent video again.
I have one suggestion/request: can you make the font size of your code a little bigger?
I am watching on a MacBook Pro 15 inch and it's kind of ok though a tiny bit small. But I find it very hard to watch on smaller screens like iPads because the font scales down with the dimension of the video.
Thanks again for the videos. I enjoy your informative and entertaining style.
Gilles

[ingongoyama]

That is a damn good camera! what model is that?

[kimberlynorton]

What software are you using to show the screen with?

[david-tracy]

Hey, serious question. What’s the benefit of using UInt here instead of Int? I’m sure you had a reason

[krutomjer]

Thanks for the video my man, I explained binary search to my gf today based on your video :)

[TheAlderFalder]

So you are basically calling the function in its own definition, making it loop through itself as many times, as the argument number and each time multiplying by the product of the previous loop. Mind is blown, loving it!

[karimgucci]

how about going through project euler problems and walk us through solutions, that would be awesome

[kimberlynorton]

Could any of you find the source code?