M.A.H.M.O.O.D's blog

2D-segment trees and quad trees
By M.A.H.M.O.O.D, history, 7 years ago, In English

Good day everyone.

Today I was trying to solve a problem that required 2D segment trees so I tried to learn them. I didn't get enough resources and the ones I got I didn't understand.

I have encountered the word 'quadtree' a lot so I have a couple of questions.

Could somebody tell me the diffrence between quadtrees and 2D-segment trees or are they the same? and could somebody point me to an article the explains 2D-segment trees well enough to be understood by me. Or can someone explain it here please ?

Thank you for reading.

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7 years ago, # |
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hello, I can surely help you.

http://codeforces.me/blog/entry/55286

I will explain the quad-cut tree in next tutorial, and also difference b/w these two data structure. Give me some time. :)

Till then, I can tell you that there was one on stackoverflow, which was explaining quad-cut tree. and it's complexity.

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    7 years ago, # ^ |
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    Thanks, your video is awesome I understand the concept behind it now.

    btw Can you use lazy propagation on 2D-segment trees ?

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      7 years ago, # ^ |
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      Could you please share the link of the problem you were trying to solve? Thanks.

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        7 years ago, # ^ |
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        Problem.

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          7 years ago, # ^ |
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          I actually solved this in O(n4). 2D prefix sums suffice for a solution in O(n2).

          Lazy propagation cannot be done in 2D. (But you can do 2D rectangle sum updates with BIT).

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      7 years ago, # ^ |
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      I will try. Right now I am outside. and Might be busy for next few days as well. I will try my best :) .

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7 years ago, # |
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Quad tree is usually not the right answer, it takes O(n log n) worst case (imagine querying the upper most line of length n), 2d seg takes (log^2 n) worst case.

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