Introduction to Recursion (Data Structures & Algorithms #6)
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- เผยแพร่เมื่อ 15 เม.ย. 2018
- Recursion explained. Java & Python sample code below.
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Find sample code in Python and Java here: www.csdojo.io/recursion
This was #6 of my data structures & algorithms series. You can find the entire series in a playlist here: goo.gl/wy3CWF
You can check out my video about dynamic programming here: • What Is Dynamic Progra...
Also, keep in touch on Facebook: / entercsdojo
If you want to find my introduction to recursion, you can check it out here: • Introduction to Recurs...
Here's my answer to the frog problem at the end: th-cam.com/video/5o-kdjv7FD0/w-d-xo.html
how does function continues to call itself in return statement , im confused because return means stop!
please explain bro
Thank you so much.You rock
I'm late but here goes:
yes, the return statement means 'stop', but stop once all code is run and your result is ready. because you're making a function call, your code will return the END of that function call. so it will go as far as the final return and then return the final result AFTER all function calls have been made.
so return func(n - 1) will work like this:
func(4) -> func(3) -> func(2) -> func(1) and lets just say you have a conditional that says if n
@@supamdeepbains5172 Return doesn't mean stop. It is used to return values if you have your function set up that way. Many people use it to stop the function in a function that doesn't return anything.
I Think the recursion is easy when we know the initial values we are taking and with correct logic
Recursion is fascinating but it gives me a lot of headaches. Great though.
Yeah, I struggle with it and I don't know why
Mee 2 bro
S bro, still i am struggling to understand
they made these algorithms by using the book
and
now they want us to make better algorithms without the use of books.
A good analogy that may help you is Russian dolls. Think of the recursion function as opening a Russian doll only to get smaller dolls after smaller dolls. Soon, you will reach a doll so small you can't open it. That is when the terminal condition is met and the recursion stops.
Great info! The only thing I have to add is that when it comes to fibonacci numbers and you're in an interview scenario, *always* make sure you ask the interviewer where they consider the fibonacci sequence to start. Some consider 0, 1 to be the first two numbers in the sequence, others consider 1, 1 to be the first two numbers. It reflects poorly on you if you make the wrong assumption.
I came up with 144 ways to cross the river:
Python:
def frogjumps(n):
if n > 0 and n < 3:
return n
if n < 1:
return 0
else:
return frogjumps(n-2) + frogjumps(n-1)
Though it works, I had to try it a few times, cause I cannot really get my head around it yet. But it seemed like the most logical solution and in the end it seemed to work ( I tested it till number 6, which I just did on paper). Would be great to see the more mathematical solution which might make more sense. Definitely going to see the next video.
Even though English isn't my first language, I FINALLY understand a recursion concept by this video. Thank you so much Dojo! You're my favorite teacher on youtube
by far the best explanation of recursion on youtube!!! Thank you, I was struggling to wrap my head around this, but when you walked through factorial(4) it clicked.
You should make a video of your understanding.
Same here man
literally the same here, clicked at fact(4) ... a lot of youtubers forget to go backward.. I want to know the CS behind it not just the outcome .
Great explaination! I've been struggling with the concept of recursive for a while but your video made it really clear, thank you.
Brilliant explanation.
I've looked at quite a few videos on recursions, and there are not many teachers who've mastered your level of clarity and simplicity. Your's is truly an art.
Keep them coming!
You are my favourite teacher yk.. I had been troubling solving recursion questions..but u cleared its fundamental concepts so well.thanx.
You are a great teacher. Congrats and thank you for helping me understand a bit of recursion!
This is the best explanation I have seen of recursion after attending a lecture, reading 3 articles, and 4 other videos!! You are awesome dude!! I am freaking subscribing!!
Hey everyone! In case you’re curious about why 0! = 1, I’d recommend Numberphile’s video about this topic: th-cam.com/video/Mfk_L4Nx2ZI/w-d-xo.html
Hello YK, please make a video on - "What kind of projects to make to get job at top companies"
Please make videos on how to get into big 4 companies. Their interview process and other stuffs.
Why not if(n > 0)?
Glenn Miller if n
U being a great Teacher ..lots of respect and love from India
You are the most effective instructor in DS & Algorithms I've listened to so far. Thank you so much!
Thank you, your videos has awaken the love for programming once more. Greetings from Colombia
I just want you to know that this is the second video from your channel that my professor has added to online CS course at a public college. I appreciate the way you teach.
what is the prog lang used in this series
@@syedabdullahatiq8125 Java
@@syedabdullahatiq8125 java, python, and c
Man, you are amazing, especially in explaining topics that require a lot of examples to understand. thanks a lot, you just earned a sub!
Excellent job in explaining recursion by implementing theory with code! Great step-by-step example!
Cs dojo. You are awesome man and the way you explain programming concepts is like anybody can code after watching your sessions...
Recursion used to be a nightmare for me.. now the concept is clear.. thanks alot .. kindly bring tutorials for arrays application using example codes
Hey Dojo, glad you're focusing on higher difficulty topics, there aren't as many that explain as well as you do.
The simplest explanation i have ever seen about recursion. Thanks a lot.
Not skipping ads to give back to CS Dojo. You're an awesome teacher!
Amazing content! I had trouble getting my mind around Recursion and your videos helped a lot along the way. Thanks a lot!!!
Good recursion example showing what happens in the stack with the actual calls of code. I've watched a lot of videos that gloss over the stack call without explaining or showing what happens, so this was incredibly useful. Thank you.
men you're awesome, I not even a English Native and I understand more from you than my courses of Algotihms. Keep going!!!!
You are brilliant !!!! could not undestand after two hours of class and you clarify everything un 22 minutes !! you are a beast!!
Thank you so much for the great video!Keep them coming!
Great job on this topic. I didn't even need to watch the second half of the video after how well you explained the factorial implementation.
Looking forward to tutorials on graphs! It's really difficult to find videos where you like both the way of teaching of the concept, as well as the fast pace of learning. My finals practical will probably be long past by the time a graph video comes up, but it just shows that how much me, and a lot of people probably, will still watch your videos ^^
And if you actually notice this question, then I kinda wanted to ask which of the data structures would you be covering in the future? Would love to watch advanced concepts like heaps and disjoint sets as well.
There are a lot of explanations for recursion but I think yours is probably one of the clearest. Good job bro.
Sad part is that these kind of talented people who can make you understand concepts as easily as that are not working on colleges, they are on top companies giving them all their talent.
To be fair though, those top companies pay them more than many colleges would.
yes colleges don't pay well sometimes
Thanks man. I didn't really understand the CS50 tutorial for recursion so this helped me enough to go back to the CS50 video and totally understand it. Keep it up!
1same here
Amazing teacher and layout compared to other videos. Thanks for this!
I had to watch your videos to finally understand recursion. Please do more videos on basic algorithms and ds, you are a genius!!!! PLEASE!
Thanks YK,u r a lifesaver.I was learning abt recursion this afternoon and I don't understand it and I ve been disappointed but now I understand it well.Lots of love and respect 🍁
CS Dojo, you are AMAZING!!!!! Thank you SO MUCH for your channel! I am DEFINITELY subscribing!!!! :)
You are the best teacher I have ever meet, just wanna say thank you Professor Dojo
You're so talented! You explain so simply! Thank you so much!
I finally find the problem of my mindset when dealing with recursion. Thank you sooo much!
Super clean explanation of the flow of recursion
This is the best Video that I have been seen about recursion.
Hey dojo.... get a series on algorithms....much needed
Btw great work!!!!
You're killing it bro!
Thank you so much. I was struggling so bad with recursion.. this video was so helpful.
Love the way you narrate. Kuddos👏👏
Great content! Love the series
life-saver!Thanks you for the clear explanation!
I love it how did you explain Recursion algorithms :)
wow your teaching style is great! thanks!
You are an excellent teacher and I finally understand recursion a bit better!
Here is my recursion solution for the fibonacci sequence (when you told us to give it a go):
def fib(n):
if n>=3:
return fib(n-1)+fib(n-2)
else:
return 1
I was so relieved when the code worked as it took me forever to get it right!
DUUUDDEEE THANKU SO MUCH!! It all makes sense now!!
This was a really helpful video. It was hard to get my head around but this video made it a lot easier. Thanks
man, you are amazing, grettings from chile!
awesome series
I was just thought the way CS Dojo has solved the fibbonacci problem is not the efficientiest way, just then he mentioned about dinamic programming that I hadnt knew. Great, thanks.
Dear CS Dojo, thank you for rescuing my life! many greetings from zurich.
very helpful and clear explanation step by step, thanks!
great explanation and break-down. thank you for this
thankyou very much for making free lessons, it's very helpful to me, never stop for doing this..
solving these problems gives massive satisfaction :)
thanks YK .
Nice explanation, cleared everything for me!
wow what an explanation
clear and precise
Excellent explanation, you are clearly incredibly intelligent and you know how to relay that knowledge as well!
Very clearly and easiest way explained. It is similar process in loop function if I'm not wrong. Anyway got very clear in recursion:) Thank You and keep going;)
Best explanation of recursion for me.
Thank you so much, I'm starting to grasp this concept❤.
Excellent video. Thanks!
thanks buddy...You are really hopeful...I am your regular some kind of fan..i am learning python from your video.thanks buddy
The imagery of recursion in my head is so satisfying. It’s like the computer opening a larger and larger function until it reaches the else statement and then closes it. It’s kinda like that domino thing where they all fall on to each other initially, and then when it hits the end they all fall again
This guy has excellent explanation skills
Amazing video as usual
Very cool bro! Keep going.
very cool video, taught me a lot about recursion
Great explanation!!! Thank you
I tried to solve the exercise, this was my solution in kotlin:
fun fibRec(position: Int):Int {
return if(position
Thank you so much sir....I'm always waiting for your videos..please don't stop your teaching sir...its my humble request...
JESUS! This is the first time that i can code fibbonacci within 10 seconds! Thanks man!
Dude...you are the greatest...
Very clear explanation, thank you
THANK YOU SO MUCH I'M CLEARLY UNDERSTAND THIS
Thank you soo much... I am a freshman CS student and I don't understand anything my prof is saying. You are videos are really clear and easy to understand. Please make more videos on Data Structures and Algorithms.
Thank you for your explanation. I think the mathematical explanation in the beginning helped a lot to really understand, what the recursive function really does.
I didn't understand, that the function is calling itself till the if statement becomes true.
i can't imagine what a wonderful teaching you are really better than my teacher .
Awesome video thank you very much!
Thanks, for great explanation!
Thank you for showing how to break down the problem :)
This is really amazing stuff especially for a self learner
love the way u explain!
even though english is not my native language i can understand ur concepts very easily..tq for ur fabulous explaination
Sir... Please continue this series in detailed. For explaining some data structure examples my preference for the language used is to be JAVA .
i freakin love you!! that shit made no sense to me in class
Great Explanation
Awesome video and explicitly clear explanation . One request can you make videos on specific language like Java for example
Great tutorial! You are awesome.
a great example of how recursion works programmatically, it solved it in my head though
def fibSeq(n):
a = 0
b = 1
for i in range(2, n):
c = a + b
print(c)
a, b = b, c
fibSeq(100)
The best video if you want to understand recursion for real!
static int fib(int n) {
int count = 2;
int first = 1;
int second = 1;
int next = 0;
if (n == 1 || n == 2) {
return 1;
}
while(count < n) {
next = first + second;
first = second;
second = next;
count++;
}
return next;
}
Here's my code. Thank you CS Dojo for all the help so far!
def fibSeq(n):
a = 0
b = 1
for i in range(2, n):
c = a + b
print(c)
a, b = b, c
fibSeq(100)
Nicely taught brother it was very clear to me thanks
Great video. Thank you so much