Editorial for GlobeX Cup '18 J3 - Good Numbers


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Author: Ninjaclasher

For each integer, x, we can loop from i=2 to i=\sqrt{x}, and check if x is divisible by any i. If it is divisible, then x is not a prime. Otherwise, it is.

We can then sum up the digits, and perform the same prime checking.

If both checks are satisfied, then x is a good number.

Be wary of x=1, as 1 is not a prime.

Time Complexity: \mathcal{O}(N \sqrt{\max{x}})


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