Comparing Iterative and Recursive Factorial Functions

Comparing iterative and recursive factorial functions

[@DJ-wu9yi]

Just had one of those "Oooooooh" moments. Thanks Khan!

[@sanketkumar9058]

Ohhhhhh, not ooooh

[@Silver-nm2if]

lol same

[@shreyashkashyap]

Thanks a ton Khan Academy. Idk why your videos don't get much views but your quality of teaching is remarkable! This is much better than the colleges/universities, that's why Elon Musk us with you guys😉

[@vinlacey]

Absolutely wonderful explanation of recursion. Well done!

[@gexwing]

it works this way: the function is still running while it calls the next function, so it builds up a stack of function calls (thus: call stack), then when it reached the base case, it returns a value, then the above returns, etc. etc. until the call stack has been reduced back to the original function call, which then returns the result, done. the variable number is NOT the same for all the function calls, each function call has its own variables.

[@Sauravkumar-co7hg]

Thank you for ur 8 y/o comment..

[@slowcreep6978]

This was the piece I was missing, thanks.

[@RUCER3Al]

I love the concept of Programming. But I really hate the method my college book is explaining this. Thank you Khan Academy!!!

[@rockingamingwiththesahit2145]

Textbooks always show thing in the hard way and not really helpful except for problems,in contrary to SK

[@jakeambrose4294]

the way you write it and show it here was enlightening for me

[@myne4]

Recursion blows my mind.

[@thepr1ntgnome430]

Yeah I know what you mean, but the process in real life is just too slow. Iteration must be better.

[@shreyashkashyap]

Same here.

[@shreyashkashyap]

@@thepr1ntgnome430 but it's more efficient and it requires much less code lines as compared to iteration method. It sure has its own advantages at many points.

[@nawfaljafri]

so basically (i think, idk cuz I'm just watching this video for fun, i dunno much about coding so correct me if I'm wrong) for 0, we specify that if product = 0 or less, then return product = 1 since a 0 in this formula would mean 0(0+1) which is 0x1=0; what's happening is basically we take an integer (integers start from 0 unlike counting numbers that start from 1) and we put it in the formula 1(i+1) where i is the integer and the 1 outside of the parenthesis is the previous product/factorial since the product of 0 factorial is 1, we start with 1; as it iterates, the previous factorial product becomes the new product outside of the parenthesis we're trying to find so we continue doing this for the number of times we want a factorial for so 3! would be 6 because 1(0+1) = 1, 1(1+1) = 2, 2(2+1) = 6 so the to calculate the factorial we could also do: def factorial(number): if number

[@mohchoudhary]

YOU'RE AWESOME, THANKS!!!

[@candichiu7850]

Thank you! very clear.

[@SB-ig1rg]

Veeeryy cool job man, big thanks to you✌️

[@spirituelconnexion]

Sal, watching this playlist makes me want to switch my major to CS :(:(:(

[@bir_deb]

Boom boom! Why is it so cutely explained!

[@DualSignal]

This video doesn't provide any comparison like the title says. It's more of a walkthrough of an iterative and recursive example.

[@JollyBeJolly]

An Iterative solution uses a loop and computes as it goes. Recursive breaks a problem down into smaller problems and calls itself for each of the smaller problems.

[@Huncho0]

@@JollyBeJolly good one - imma add that to my notes thanks!

[@xWaterTwist]

@@JollyBeJolly That was such a good explanation thanks

[@petruciucur]

Very well explanation. So the program stacks the numbers n in memory then go back and solve each multiplication.

[@k12_hnbuihuyhoang51]

Thanks god you're here.

[@RiyadhElalami]

I love this guy

[@serenity3270]

note, that i + i should be i + 1? yes?

[@Nopalesasados]

Thank you.

[@sophia0282]

Thank you sir!

[@majesty1396]

thanks a lot

[@lolk191]

hey tech me if we put njmber=1 in if statement so ans is 1 how

[@kerrywsmyth]

I would never guess recursion would ever work because it APPEARS as if you are redefining the value of the variable "number" and returning a result every time the function recurs. The thing that needs explaining for me is how Python knows to remember each of the returned results for each recurring function call.

[@B1GL0NGJ0HN]

You need to learn about the “stack”. When new functions get ran, all of those variables are put in a new place in the “stack”. Stack and heap. Different memory allocations.

[@tubex1300]

can u recommend the books about the iteration

[@AlderDragon]

@radiator0505 I think it has to do with the definition of a factorial. It works fine when the numbers are decreasing, but the definition of a factorial given a negative number is different (since the numbers are increasing each time rather than decreasing).. this results in a divide-by-zero error when you get to 1. Why the program returns 1 I am not sure.

[@ferhatakbulut6572]

You are absolutely right sir, also going to zero makes no sense since you are multiplying because after that your value would be always 0 since you multiplied by a zero once.

[@victornnah3920]

Must I always return 1

[@djbvon6769]

I have to admit, almost went to another video after hearing a mistake in the "iterative" pronunciation within the very first verbal audible of this video.

[@weiliantan4386]

What does return do ?

[@hassanshabbir8254]

It is a python keyword referring to the output of the function.

[@riteshsaha9729]

which function is faster?

[@gardenhouseNemurin]

Late response but iteration is generally faster, although the difference only becomes noticeable as you increase the number of iterations/recursive calls you need to make. Recursion creates unnecessary overhead as you need to keep multiple calls open until you reach a base case, which can easily deplete the resources of a less powerful machine. A well optimized iterative solution always beats a well optimized recursive one (even if you use memoization), because it does not have to deal with the extra overhead of keeping recursive calls open.

[@bara7979]

Missed your sound❤

[@moliv8927]

not the comparison i expected ...

[@Lundburgerr]

python is the shit!

[@ujjvalw2684]

Who is this Teacher?

[@danielford2898]

Chaos

[@phazon100]

second. lol

[@SarinaSaman]

recursion is a billion times better than iteration tbh

[@Sauravkumar-co7hg]

How is that so.?? Recursion takes a lot of memory

[@gardenhouseNemurin]

It's sometimes easier to come up with recursive solutions for some problems (e.g., given a positive integer n, finding the n-th element of the Fibonacci sequence.) However, as the number of recursive calls increase, so does the overhead of keeping those calls open, which makes your program use more resources than it really needs to. Even if you use memoization, iteration is generally faster and consumer less resources as everything is contained in a single call.

[@MarsTheProgrammer]

you can't explain recursions with functions in 2 minutes...