It would be better to add squared integer numbers n in the test suite, in which case, the number of divisors is odd. However, the test suite only contain non-squared integer n, in which case the number of divisors is always even.
Any particular reason why sqrt is forbidden?
The divisors are symmetric about sqrt(n). I guess the intention to forbid sqrt might be to eliminate brute-force search approaches, which need to search over 1~sqrt(n).
Peng Liu ,thanks for the suggestion.I added a few tests.
James, the reason sqrt is forbidden is what Peng Liu suggested.
Hey, this problem is essentially the same as problem 2664 by Jean-Marie.
It is not good idea to use arrays from 1 to n.
nice! really nice.
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