reversebinary spotify puzzle. https://www.spotify.com/int/jobs/tech/reversed-binary/

reversebinary.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
Reversed Binary Numbers
~~~~~~~~~~~~~~~~~~~~~~~
Yi has moved to Sweden and now goes to school here. The first years of
schooling she got in China, and the curricula do not match completely in the
two countries. Yi likes mathematics, but now... The teacher explains the
algorithm for subtraction on the board, and Yi is bored. Maybe it is possible
to perform the same calculations on the numbers corresponding to the reversed
binary representations of the numbers on the board? Yi dreams away and starts
constructing a program that reverses the binary representation, in her mind. As
soon as the lecture ends, she will go home and write it on her computer.

Task
Your task will be to write a program for reversing numbers in binary. For
instance, the binary representation of 13 is 1101, and reversing it gives 1011,
which corresponds to number 11.

Input
The input contains a single line with an integer N, 1 ≤ N ≤ 1000000000.

Output
Output one line with one integer, the number we get by reversing the binary
representation of N.

Sample input 1    Sample output 1
13                11

Sample input 3    Sample output 2
47                61
"""

from functools import partial

to_decimal = partial(int, base=2)


def to_binary(number):
    if number == 0:
        return ''
    else:
        return to_binary(number // 2) + str(number % 2)

if __name__ == '__main__':
    import sys
    for line in sys.stdin:
        print(to_decimal(to_binary(int(line))[::-1]))