Number of Islands - Leetcode 200

Number of Islands - Leetcode 200

[GregHogg]

Learn Data Structures & Algorithms for FREE at AlgoMap.io!

[davidshipman]

When I helped a senior engineer interview some candidates, he always asked this question.

[Matrixerqwerty]

I literally just solved this
But this method is much more efficient
Thanks again Greg 😊

[samarth]

Uncle, you're video helped me a lot. Thanks ya❤

[ceciljoel]

This problem was in a codeforces contest too

[blazingazong]

Can I… approximate? With something like a kernel convolution as the basis for finding edges?

[beaf]

haha i had to do this in a game to make sure the player only built one "island" perse, i just rawdogged the search algorithm and it turns out to work.

[Sluggernaut]

Fuzz buzz is the most asked question in interviews

[Chronologist]

I remember back in the day I was optimizing a connected component clustering algoritm and tried to get labs from a connectivity matrix as fast as possible. I faintly remember that the best solution was to do a QR decomposition of the matrix. However, I did it in Matlab there was some speciality that it returned some row order array which was what I was looking for right away. Some day I should try to recreate my code and probably have a lool at Lapack and see what was actually going on :D

[eric]

Very fun problem, one of my favorite dfs questions

[neevpenkar]

I think this can be solved very similarly to 'bwlabel' in MATALB - using the Two - Pass algorithm. On the first pass label every 1 and write down equivalencies, then on the second pass just relabel according to the equivalencies.

[kho-uw]

wouldn't disjoint sets be better?

[luan]

I was going to do it differently,
Make a counter set to 0, loop over each element, if 1, check (i-1, j) == 1or (i, j-1) == 1, if not, add to counter, if yes, skip

[spacey]

And to use O(1) memory you can write 2 instead of 1 for the islands. Now you know what vertices you already visited.

[Karthikeya.A]

You reversed row and column, rows are horizontal.

[егор-шоз]

Why do you say there are three islands here if there is only one island?

[lbozbabyjsus]

What's the answer?!? Haha you could have posted it for a blip so i could look over the code! I'm not even sure you can solve it based on this video, so today, I will not be purchasing or looking at your videos.

[mhalton]

Given the explanation, there's really only ONE island.

[shirakuyanai]

Yeah but in case of
[1, 1, 0]
[1, 0, 0]
What do those 1's make? Gotta be more specific on the conditions.

[ujjwalaggarwal]

Solution :-



print("total islands = 3"). 😂