codewars：the supermarket queue

有段时间沉迷在codewars刷题，现在趁着有博客了把这道题记录下来

There is a queue for the self-checkout tills at the supermarket. Your task is write a function to calculate the total time required for all the customers to check out!

The function has two input variables:

customers: an array (list in python) of positive integers representing the queue. Each integer represents a customer, and its value is the amount of time they require to check out.
n: a positive integer, the number of checkout tills.
The function should return an integer, the total time required.

EDIT: A lot of people have been confused in the comments. To try to prevent any more confusion:

There is only ONE queue, and
The order of the queue NEVER changes, and
Assume that the front person in the queue (i.e. the first element in the array/list) proceeds to a till as soon as it becomes free.
The diagram on the wiki page I linked to at the bottom of the description may be useful.
So, for example:

queue_time([5,3,4], 1)
should return 12
because when n=1, the total time is just the sum of the times

queue_time([10,2,3,3], 2)
should return 10
because here n=2 and the 2nd, 3rd, and 4th people in the
queue finish before the 1st person has finished.

queue_time([2,3,10], 2)
should return 12
N.B. You should assume that all the test input will be valid, as specified above.

P.S. The situation in this kata can be likened to the more-computer-science-related idea of a thread pool, with relation to running multiple processes at the same time: https://en.wikipedia.org/wiki/Thread_pool

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def (customers, n):
    l=[0]*n
    for i in customers:
        l[l.index(min(l))]+=i
    return max(l)