Technical Interview Question: Number of Islands [LeetCode]

In this video, I explain the popular coding interview question Number of Islands.

This problem is asked at Google, Amazon, Facebook, and many other companies.

The idea behind the algorithm is to use a DFS traversal to change all land to water. Each time we encounter land, we will tally up how many islands their are. This problem can be solved using a BFS or Union Find algorithm, but I find the Depth First Search solution the easiest to understand.

[usmanh]

I just went through all the big youtubers who explained this, and you explained it the best, yet you have the least subscribers - please, I urge you to keep going, you'll gain traction soon, really great quality stuff, good job!

[pogostemoncablin]

I can't thank you enough, you are a great teacher. I am learning graphs from you and I'm getting over my fear of graphs because of you.

[koredyte]

Best video on this topic. I particularly like the 'sink' analogy, and also the fact you took the time to explain the problem in detail first!

[robertsedgewick]

Many explanations on youtube for this question, but this is by far the clearest! The specific naming of changeLandToWater( ) makes it so much clearer compared to dfs( )

[panzabamboo]

Best vid I have seen on this, thanks!

[dimejifaluyi]

Really great explanation. By 4:31 I knew where you were going and had that 'Ah ha' moment and was able to implement it from there on. Thanks!

[majetyprashanth]

Never understood this problem's solution this clearly ! You've explained every single small step in detail .. I'm really glad to have found your channel ! Keep going !!! ^_^
At the end, I was like this problem is so easy and I could not believe that the solution was so easy using recursion. All
thanks to you brother :)

[Dragondavid]

Man you finally made me to understand my hero!!

[johnkim]

This is a really good explanation! Great job doing in !

[soumilmishracomp]

The video is really helpful. Keep up the good work and I request you to please draft some more similar videos for other leetcode problems.

[krishika]

Best explanation on this topic! Loved it (y)

[Anand]

Hey Michael, Thank you for this amazing playlist. As I see the maximum questions in the playlist is consist of DFS. Can you make some set of questions where we need to apply BFS and show us how to apply?

[snigdhapurohit]

Thank you so much for explaining this problem so well. :)

[anpascally]

Great video, great explanation. Thank you so much.

[dustinv]

Great video. Thanks for your clear explanation.

[KnowledgeAmplifier]

Very nice explanation ... Clear idea:-)

[woodylucas]

Every time you ever go over a problem I say to myself "Why did I ever struggle?"

[ShashwataSaha]

For the same algo it's saying maxing recursion depth excided, In pythn

[subhadeepbhattacharyya]

I am not sure if your up and down notations are correct.

[vincenr]

Nice! You should create more videos like this but with other problems. 👍🏻