nchn27's blog

By nchn27, history, 6 weeks ago, In English

We have an array of (10^5?) integers and we have to count the number of subsequences of length 3 that are also arithmetic progressions. I believe they also have to be in the right order.

I googled so hard but I forget the problem name and solution. The problem should be on CodeForces. I vaguely remember a cool solution involving hashing?

Can anyone please help me find the problem / solution

 
 
 
 
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I guess you're talking about this one (even though it's for a permutation).

452F - Перестановка