CODEWITHSUNDEEP
pythonpython-3.xbit-manipulationbit
topkek
topkek

Reputation: 169

How do I find the position of the least significant bit in which 2 numbers differ in python?

I have two binary numbers 

01110

and 

10010

It is easy to see that the first position they differ is the third from the right. How do I find this in python? Let's say, I would hve something like sdb(a, b) and that would return 3 in this case. Are there better options than looping over the 2 number's bit from the right using leftshift?

Upvotes: 1

Views: 231

Answers (1)

Chris Doyle
Chris Doyle

Reputation: 11992

you can XOR the two numbers and XOR will return 0 when both bits are the same and 1 when both bits are different. so the result of 01110 ^ 10010 will be 11100 we can then parse this as a string using rindex to look for the first 1 we encounter from the right hand side as this will be the first place the bits were different. This will give us the index from the left. we then subtract this from the length of the xor string to get the bit count from the right where the difference occurs.

def sdb(a: int, b: int) -> int:
    try:
        xor_string = f'{a^b:b}'
        index = len(xor_string) - xor_string.rindex('1')
    except ValueError as ve:
        #if no bits are different return index 0
        index = 0
    return index

num1 = int('01110',2)
num2 = int('10010',2)
print(sdb(num1, num2))

Upvotes: 3

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