CODEWITHSUNDEEP
pythonfunctioncountbit
PineNuts0
PineNuts0

Reputation: 5234

Python: Trying to Count Number of 1 Bits in an Integer But Missing One 1

Input: n = 00000000000000000000000000001011
Output: 3
Explanation: The input binary string 00000000000000000000000000001011 has a total of three '1' bits.

When I run my code below it appears that only two 1's are recognized ... why is that?

class Solution(object):
    def hammingWeight(self, n):
        """
        :type n: int
        :rtype: int
        """
        
        sum = 0
        
        for i in str(n):
            sum += int(i)
            
        return sum

enter image description here

I think I'm misunderstanding some concepts here. Would appreciate some guidance.

Upvotes: 0

Views: 1614

Answers (2)

Michał Šrajer
Michał Šrajer

Reputation: 31182

change str(n) into bin(n)[2:]. This way you will get binary representation string of n with omitted "0b" prefix.

BTW, you don't need to count manually in a loop. Python string has .count():

return bin(n).count("1")

Upvotes: 0

HTF
HTF

Reputation: 7280

Python 3.10 introduces int.bit_count() but if you have to implement the algorithm yourself then you can try something like this:

test.py:

def count(n):
    bits = 0

    while n:
        bits += 1
        n &= n - 1

    return bits


def main():
    n = 0b110001010000000000111
    c = count(n)

    print(f"Bit length: {n.bit_length()}, bits: {c}")


if __name__ == "__main__":
    main()

Test:

$ python test.py
Bit length: 21, bits: 7

The time complexity of this algorithm is O(k) where k is the number of bits set to 1.

Upvotes: 3

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