I should have a complete array of numeric identifiers like this one:
a = [3, 4, 5, 6, 7, 8, 9, 10]
But instead, I have a a messed up array in random order, with duplicates and missing numbers like this one:
b = [4, 9, 7, 7, 3, 3]
Is there a more optimal way to find out which numbers are missing apart from substract the array without duplicates?
a - b.uniq
Ruby 2.6 introduced Array#difference which seems perfect here:
a = [3, 4, 5, 6, 7, 8, 9, 10]
b = [4, 9, 7, 7, 3, 3]
a.difference(b)
# => [5, 6, 8, 10]
Seems handy for this, with the added benefit of being very readable.