generate all n bit binary numbers in a fastest way possible

Question

How do I generate all possible combinations of n-bit strings? I need to generate all combinations of 20-bit strings in a fastest way possible. (my current implementation is done with bitwise AND and right shift operation, but I am looking for a faster technique).

I need to store the bit-strings in an array (or list) for the corresponding decimal numbers, like --

0 --> 0 0 0

1 --> 0 0 1

2 --> 0 1 0 ... etc.

any idea?

Answer 1

Python

>>> n = 3
>>> for x in range(2**n):
...   print(f'{x:0{n}b}')
...
000
001
010
011
100
101
110
111