Data Structures and Algorithms in Ruby: Linked Lists #2

In this linked list video we implement the prepend and remove methods which allow us to add a node to the beginning of our linked list and remove a node from our linked list.
If you haven't watched it yet here is a link to part 1 of this video series: • Data Structures and Al...

[@santaclause1988ify]

More data structure and algorithm videos please

[@connerjensen8170]

More videos on ROR and Ruby to come! Please let me know if you have any video suggestions. Thanks for watching!

[@yasinowen]

Create a top level crud api and tricks

[@yasinowen]

next video RoR tricks.

[@jetspray3]

And just a few months ago I learn there is an implicit self created if you used an instance method in another method. It makes me reflect on the implicit return created at the end of a method.

[@VictorBStan]

Also, if you're working with adding and removing values, you could potentially add the same value multiple times, then remove one of them, but still find that you have a node with the same value. maybe that's a feature, maybe that's a bug, depends on how you might use your linked list. another options is to use 'indexes'. so you can insert values in between nodes as well. just some thoughts. There are many ways to implement linked lists :)

[@connerjensen8170]

Awesome suggestions and thoughts Victor! I appreciate your feedback.

[@GokuSan389]

Hello, nice videos. Just a small tip :) I believe you could, instead of always calling Node.new(value, nil), assign nextNode = nil in initialize method as default value. Also a question why do you have class in class ??

[@connerjensen8170]

Yes, you are right. Thanks!

[@chantalwobben7518]

Maybe a idea for video 3 how to reverse a linkedList ?

[@RR-et6zp]

Can you explain what a node is? and what an edge is ? is it like the title of the data structure ? how stuff interacts with each other

[@sidduh5607]

I think in remove method, we need to make self.head = node.nextNode if we are trying to remove first node.

[@ritikagakher9688]

More DS videos please 🙏

[@connerjensen8170]

Long time off, but working on more content now!

[@ulyssebuonomo4148]

Prepend could really be a one liner, no need for nil check. self.head = Node.new value, head

[@jazthomson1171]

Sorry but I think there might be a bug in your remove method - if you remove the head when there are more nodes after it, how will you manage to traverse to those nodes? Perhaps I am misunderstanding. Nice video regardless :)

[@GokuSan389]

I second that. He has a bug in the remove method. I have implemented a print_list method and it stops due to the return if head.nil? It should be return self.head = node.next_node if node.value.eql?( value ) So first you set node = head than prev_node = nil and than the return and than the until loop....

[@connerjensen8170]

Yes, you are right. Sorry about this error

[@VictorBStan]

Also curious, maybe someone already mentioned, but it's common to use @val (instance variables), self.val usually used for class variables. attr_* gives you the methods to get/set instance variables on an object, so in initialize just use @val and @next_node; then you can just say object.val/object.next_node and object.val = 'val', object.next_node = 'val'.

[@MoeNegm]

so i tried this and i think there is a bug in your remove method. here is my test: ll = LinkedList.new ll.add(10) ll.add(20) ll.prepend(5) puts ll.head.value #5 puts ll.head.nextNode.value #10 puts ll.head.nextNode.nextNode.value #20 puts ll.find(10) #true puts ll.find(50) #false puts ll.find(20) #true puts ll.find(50) #false puts ll.find(10) #true ll.remove(5) puts ll.head.value #undefined method `value' for nil:NilClass puts ll.head.nextNode.value this is not working for when you remove the first node in the list, it does work if i remove the second or third. but not the first

[@MoeNegm]

here is how i solved it: def remove(value) return if head.nil? node = self.head prev_node = nil return self.head = self.head.nextNode if node.value == value while node && value != self.head if node.value == value if prev_node prev_node.nextNode = node.nextNode return else self.head = nil return end end prev_node = node node = node.nextNode end end

[@MoeNegm]

thanks to your two videos, i feel comfortable enough with nodes now where as they were a complete mystery before. Keep up the great work, I'll be subscribing.