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Mo's Algorithm on trees
By virus_1010, history, 7 years ago, In English

I did the problem COT2(http://www.spoj.com/problems/COT2/) using Mo's Algorithm on trees....Wondering if a solution faster than n*sqrt(n) exists?

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7 years ago, # |
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Good day to you!

Well I've done that with MO and it passed (AC).

For MO, follow this tutorial.

Then for each "move" (i.e. increase/decrease boundary of array) you shall be constant [O(1)]. The same is possible for answers.

A very good manner might be to "rename" all numbers so they will fit to 0<= Ai <= N (just sort them and rename them to indices), so you can simply operate over array.

Next thing is to choose good SQRT. Even though I guess any "normal" would do so, I've solved it with "(222)"

So the final complexity was O(Nsqrt(N)) [i.e. no maps, and no other logarithmic operations during MO]

Good Luck & Have Nice Day!

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    7 years ago, # ^ |
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    Sorry for a bit confusing language, I was asking if a solution faster than n*sqrt(n) exists or not.. Sorry for inconvenience :)

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      7 years ago, # ^ |
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      Oh I'm sorry (misunderstood that Nsqrt(N) was not enough)

      Well don't know about any :'(

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7 years ago, # |
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Auto comment: topic has been updated by virus_1010 (previous revision, new revision, compare).

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7 years ago, # |
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Am I wrong that you are asking a question related to this problem that is one of problems from a running contest (CodeChef February Challenge 2017)?

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