The question explains -

Given n = 2, return 91. (The answer should be the total numbers in the range of 0 ≤ x < 100, excluding [11,22,33,44,55,66,77,88,99])

I think it should be -

Given n = 2, return **90.** (The answer should be the total numbers in the range of 0 ≤ x < 100, excluding [ **00,** 11,22,33,44,55,66,77,88,99])