Interesting Question on Co-primes

Revision en2, by darth_chef, 2020-08-22 09:25:05

I found this question somewhere online, which went as follows: For each integer x in a given range [L, R], find the count of integers in the given range that are co-prime with x. Constraints: 1 <= L <= R <= 1e5

Example: For L = 2, R = 4, the co-prime pairs would be:

2 -> (2,3) so count = 1 3 -> (3,2), (3,4) so count = 2 4 -> (4,3) so count = 1

Does anyone have an optimal solution for this?

Tags number theory, gcd, coprime

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en2 English darth_chef 2020-08-22 09:25:05 156
en1 English darth_chef 2020-08-22 09:17:30 336 Initial revision (published)