welldone!

well needed some time to understand,
this is fkn genius ngl

a monstrous complication from scratch

That's Java 11 or later

That is short and effective solution, instead of looking for minimal and maximal values you gust sort array. And alghorithms of sorting usually work faster with almost sorted arrays. So your program may be one of the quickest, even if queues are very long.

Is checking for null or returning string smaller/equal 4 must have?
I did code like this and it has no error with empty string and properly showing 1-4 character strings

You could use the string repeat function tocreatedthe masked part

here better to use StringBuilder.

put str.kength() in an integer variable for more neat code

my solution same as this, but i did not sort that result array ,so a little complect

GG, i had the same idea, but its the simple code, GGWP

What a fucking genius GG nice solution

String concatenations are expensive.

The core idea is to place each customer in the queue with the shortest processing time of all the previous queues

Excellent work!!
Even if this code is incresing complexity with increaing no of tilts, the way of thinking is appreciable...