I have tried something similar (but less elegant), however this algorithm does not pass the test with the dataset:

customers {100, 90, 90, 60, 50}
n 2

this algorithm return 210 (100+60+50 = 210 vs 90 + 90 =180)
but true result: 200 (100 + 90 = 190 vs 90 + 60 + 50 = 200)

correct me, if i am wrong. This solution takes n^2 running time due to for each customer, this program is finding the register by checking each register's least. Space-wise, it is O(n) where the n is the number of registers.

There are specifications:

input customers: an array of positive integers representing the queue.

So a (silly and absurd) input of a negative queue will never happen.

Very nice! However, it will crash when (n <= 0).

it is so beautiful and I am superised that my code is similar to this solusion ,I'm just a noob guy here XD

For those unfamiliar, the problem is also known as "Bin Packing". I was very suprised but the simplicity of solution, when I first heard about it as well :D