Diameter of Binary Tree - Leetcode 543 - Trees (Python)

[@GregHogg]

Master Data Structures & Algorithms For FREE at AlgoMap.io!

[@gaurangdeka]

Stumbled upon this after having a hard time understanding Neetcode's explanation. This is so much better!

[@KAVINSAGARR]

same here !!

[@bigk9000]

In regards to the variable scoping topic: Instead of creating a single field array, you can also use the `nonlocal` keyword as well. Though, it does add an extra line to your code, as it'll look something like this: nonlocal largest_diameter largest_diameter = max(largest_diameter, left_height + right_height)

[@DerekGomez-n1w]

I do this, too! Had to learn this the hardway haha I spent like an hour researching scoping in python and why the global keyword doesn't work

[@swapnilrao9881]

such a good explanation, i really couldnt wrap my head around the recursion until i watched this video. leetcode truly humbles you!

[@andrewbrowne8498]

You can also just use "nonlocal largest_diameter" at the beginning of the function

[@cbbforever]

the best explanation in the whole universe, and don't know why those bad solution vedio got so many views, yours deserves more. PS: I think this problem should labelled as medium.

[@GregHogg]

Awe thank you so much! And yes this should be a medium haha

[@helloworldcsofficial]

I think what trips us the most is ensuring we know the definition of height, depth, max height, max depth of a tree and/or node. In some sites, these are defined by number of edges but in others by number of nodes. Once you get these definitions right, the solution becomes even more clear. Thanks for the vid!

[@GregHogg]

Yeah for sure, totally agree. No problem!

[@servantofthelord8147]

Instead of using that list trick at the end, couldn't we just define "self.largest_diameter=0" then just use self.largest_diameter everywhere that we reference it? This worked for me : class Solution: def diameterOfBinaryTree(self, root: Optional[TreeNode]) -> int: self.max_diam = 0 def height(root): if not root: return 0 left_height = height(root.left) right_height = height(root.right) diam = left_height + right_height self.max_diam = max(diam,self.max_diam) return max(left_height,right_height)+1 height(root) return self.max_diam

[@deed.9516]

Thank you for this detailed explanation! I ran into the same error with the nested function, so I appreciate you covering that!

[@GregHogg]

Yeah that's a super annoying and common pitfall, I was confused with it for a long time too... Hopefully I helped explain that decently:)

[@ravindraramachandra2237]

Thank you... crisp and clear explanation!

[@AtharvNaidu-mh2pm]

How are you such a good teacher bro, thanks so much this explanation is awesome

[@nooraldeen6637]

Also I believe you can just do nonlocal largest_diameter inside of the height function instead of making it into a one-item list

[@GregHogg]

You could, yes :)

[@zxchh4629]

thanks a lot, by far the best solution i've seen for this one on here

[@GregHogg]

Glad to hear it, this can be a tricky one!

[@nooraldeen6637]

Oh wow your explaintations are extremely detailed and clear. Keep it up! Thank you

[@GregHogg]

For this question in particular, I'm actually super glad to hear it. Thanks so much :)

[@__chroma__8660]

I have a question. Instead of calculating the withing the height function, i calculated the diameter at the end by using diameter = height(root.left) + height(root.right). This worked for most test cases except one. Why do I have to calculate the diameter within the height function and not after?

[@moade5700]

could you please expand on why a list is accessible from the scope of the method ?

[@MamoodXx]

I just started algorithms after doing oop, I feel like Im always one step from solving the problem but I never find that step, is ok that Im going to KZbin to find the solution or am I ruining my progress. Thank you

[@GregHogg]

Looking up the solution is totally okay :)

[@chi94]

you're meant to look at the solution. How are you suppose to solve an algorithm question when you've never encountered it? Humans aren't aliens!

[@MohammedAli-p7e9d]

​@@chi94 by thinking logically 😅 I am not saying it's not ok to look for solution on KZbin or elsewhere but we should give it some tries to solve problems to strengthen our logical thinking.

[@MohammedAli-p7e9d]

This must be medium. Thanks alot for the great content.

[@siddhantkumar9492]

I believe its not required to pass the same parameter to the nested function that is already a part of the parent function, we can directly access it. Feel free to correct me if I'm on the wrong direction!

[@GregHogg]

Which parameter would that be?

[@siddhantkumar9492]

@@GregHogg I was wrong, my bad. The above logic is only applicable when that parameter doesn't change within the nested function

[@aakashs1806]

Looks like height computation

[@onurucar1112]

Amazing and simple as usual!

[@GregHogg]

Thanks so much for the support, and very glad to hear it!!

[@aradhyadhruv-y4l]

Your explanations are really good. Please make a video on LRU cache as well

[@GregHogg]

Thank you! And alright I'll do that one could be a little bit though

[@itvaya]

can you please tell me which app you are using for drawing while explaining

[@GregHogg]

I use miro :)

[@JSH1994]

please solve more problems :)