Recursive function that prints the binary representation of the integer

Question

so i have started the code, and i know that everything after the 'else' is probably wrong:

def binary(n):
    if n < 2:
        print (n)
    else:
        x = (bin(int(n)//2)
        print (x)

it should do this recursively:

>>> binary(0)
0
>>> binary(1)
1
>>> binary(3)
11
>>> binary(9)
1001

i do need the function to print the binary representation rather than return.

Solution 1

This will not work as expected, as you have print in two places, you will end up with multiple lines, e.g.:

>>> def binary(n):
...   if n < 2:
...     print n
...   else:
...     binary(n / 2)
...     print n % 2
... 
>>> binary(0)
0
>>> binary(1)
1
>>> binary(3)
1
1
>>> binary(9)
1
0
0
1
>>> binary(10)
1
0
1
0

Other answers use strings, so here's one with lists: :)

>>> def binary(n):
...   if n < 2:
...     return [n]
...   else:
...     return binary(n / 2) + [n % 2]
... 
>>> binary(0)
[0]
>>> binary(1)
[1]
>>> binary(3)
[1, 1]
>>> binary(9)
[1, 0, 0, 1]
>>> binary(10)
[1, 0, 1, 0]

and if you really want a string, it's as simple as this: :)

>>> ''.join(map(str, binary(10)))
'1010'

Of course, since you've already found out about the function bin, you should probably have done this in the first place:

>>> bin(10)[2:]
'1010'

How this reminds me of this:

• http://www.ariel.com.au/jokes/The_Evolution_of_a_Programmer.html

Happy coding! :)

Solution 2

def binary(n):
    if n < 2:
        return n
    else:
        return str(binary(n / 2)) + str(n % 2)


print binary(9)

It returns instead of prints, but usually that's better.

Comments

[Admin]

hmm i tried this, but the result i get when i try "binary(3)" is >>> binary(3) 1 'None1'

[amindfv]

@AngelE: I don't - I get "11"

[Admin]

i figured it out, i was putting print rather than return. But i need this function to print and not return unfortunately :(

[amindfv]

@AngelE: You can't just say "print binary(3)"?

[Admin]

you're answer is great! for the first solution that you provided, is there any way to make it print horizontally? i tried "print(n%2, end='') but that did not work.