There is no reason. It is redundant and verbouse.

what is the reason for assigning an alias "age" to the age table?

Thanks, I guess I should have worked that out from the example I gave.

Is is not always starting at length 1. Here it is starting at length 4.
So 5 is really the only answer. :-)

For the random tests in Java it appears to have multiple missing array lengths. e.g.
Wrong for [
[2, 2, 1, 3, 4, 1, 2, 1],
[4, 3, 4, 3, 1, 0, 4],
[2, 0, 1, 0, 0, 1],
--missing 5
[0, 3, 1, 2]
--missing 3
--missing 2
--missing 1
] expected: 5 but was 1

It is true that 5 is missing but so is 1,2 and 3. Is it expecting to receive the largest missing array?

I think the points are split between 'Code challenge completed' = 1pt and the 'colorX code challenge completed' = N - 1pt

The test based on diff'ing the output can fail if there are multiple jobs with identical salarys