Do as below using Array#permutation
:
>> a = 1234.to_s.chars
=> ["1", "2", "3", "4"]
>> a.permutation(4).to_a
=> [["1", "2", "3", "4"],
["1", "2", "4", "3"],
["1", "3", "2", "4"],
["1", "3", "4", "2"],
["1", "4", "2", "3"],
["1", "4", "3", "2"],
["2", "1", "3", "4"],
["2", "1", "4", "3"],...]
Your modified method will be :
def number_shuffle(number,size)
number.to_s.chars.permutation(size).to_a
end