If both the digit sums add up to 9, then both numbers will be evenly divisible by 9. It's not possible for the digit sum to be 0 since the inner string is always at least 1 character long.

So how to explain that
18 => (1 + 8) = 9 - the sum of the digits is 9
but
18 % 9 = 0 and 0 != 9?

thanks for asking so i didn't have to

This should be sticked somewhere... !

Nice !

Thanks for the comment. When I refactor code I try to ditch repeated patterns, I try to do this keeping the meaning clear, sometimes it works better thn others.

Because [4, -1, 2, 1] is the subsequence with the greatest sum (6) in [-2, 1, -3, 4, -1, 2, 1, -5, 4].

Any other subsequenc would have lower sum than that for example

• [4, -1, 2, 1, -5] sums up to 1
• [-3, 4, -1, 2, 1] sums up to 3
• [1, -3, 4] sums up to 2
• [1, -3, 4, -1, 2, 1] sums up to 4

So you have to find the subsequence of any length that produces the greatest sum.

None ;)