divmod_hash_inject.rb

def div_hash_inject(r)
    [10_000, 5_000, 2_000, 1_000, 500, 100, 50, 10, 5, 1].inject(Hash.new(0)){|h, d|
        a, r = r.divmod(d)
        h[d] = a
        h
    }
end
p div_hash_inject(123_456) # {10000=>12, 5000=>0, 2000=>1, 1000=>1, 500=>0, 100=>4, 50=>1, 10=>0, 5=>1, 1=>1}