real_father_of_goku's blog

Spoj INCSEQ
By real_father_of_goku, 9 years ago, In English

How can we solve spoj problem INCSEQ using segment tree?

Here is the link to the problem

http://www.spoj.com/problems/INCSEQ/

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9 years ago, # |
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I think, that you can solve this task in such way :

You will use K segment trees.

1. Sort all elements of given array in non-decreasing order.

About sort : if elements are equal — the minimal element will be element which has the rightmost position.

2. You should update every segment tree in such way : 

sum = getSumOnPositionInPrevSegTree(1, myElementPosition - 1)

3. Le'ts add the value of sum in the current segment tree in position myElementPosition.

My AC code here

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9 years ago, # |
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Another ways to solve the problem:

  1. BIT-based: d3HGAB
  2. Merge-sort based: becXSW
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    9 years ago, # ^ |
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    Can you please explain how BIT is working for this problem? Also , why we need to increment a[i] during scanning the input

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      9 years ago, # ^ |
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      Increment is because BIT is 1-based structure. Bit-based solution is simply in k turns calculate on each turn number of sequences of length i ending in pos.

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