Getting prepared for INOI

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Indian National Informatics Olympiad

Disclaimer : This post is mainly intended for an Indian audience.

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Small-to-Large

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The Vanilla Method Let's take the given problem: We have some sets as U = {S1,S2,S3....Sn} where U is the "container" set. Initially each set contains a single element. After each operation each set will contain some numbers. We define the cost of a set as the number of unique elements in the set. For each query, we merge two unmerged set and then report the sum of cost of all the sets.  The most brute force approach is for each query, add all numbers in one of the sets and put them in the other set. This will take approximately O(nlogn) time per merge operation and since there can be about O(N) mergings (because after atmost N mergings there will be only 1 set left) this will take time proportional to O(n^2logn) time. For the report, part, we just return the sum of the sizes of the set. This part is O(1) as we only have to check the size of the new merged set as the sizes of the other sets haven't changed. This is obviously a poor algorithm for a seem
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