Reverse integer digits

Question

I was trying to reverse the digits of an integer: 123456 => 654321, and the best solution that I could come up with was 123456.to_s.reverse.to_i. I feel that this is too much of code. Anyone have a better approach than this?

Answer 1

This is a very "code golf"-ish answer, and not something I'd suggest writing in real code...

But you can shave an extra character off the answer with:

123456.to_s.reverse.to_i
123456.digits.join.to_i

Or (again, only as a 'code golf' answer!!) if you're happy to end up with a String rather than an Integer, you can make this even sorter with:

123456.digits*''  #=> "654321"

In fact, converting to a string might actually be preferable, because it may prevent loosing information from missing zeros. Code-golf answers aside, compare:

43210.to_s.reverse #=> "01234"
43210.to_s.reverse.to_i #=> 1234

Answer 2

Here is another way without converting string....

x = 12345
y = 0

while x > 0 do
    y = y*10
    y = y + (x%10)
    x = x/10 

  puts y      
end

This algorithm can be asked in many interviews as well....not matter which language you use....this logic will be same. above example using Ruby