If you wish to group non-negative integers by the number of zero digits they contain, you can do this:
def nbr_zeroes(n)
return 1 if n == 0
m = n
i = 0
while m > 0
i += 1 if m % 10 == 0
m /= 10
end
i
end
numbers = [1, 3, 500, 200, 4000, 3000, 10000, 90, 20, 500000]
numbers.group_by { |i| nbr_zeroes(i) }
#=> { 0=>[1, 3], 2=>[500, 200], 3=>[4000, 3000], 4=>[10000] }
numbers = [100000, 100001, 304070, 3500040, 314073, 2000, 314873, 0]
numbers.group_by { |i| nbr_zeroes(i) }
#=> { 5=>[100000], 4=>[100001, 3500040], 3=>[304070, 2000],
# 1=>[314073, 0], 0=>[314873] }