Number of 1 Bits Python

PROGRAM TO COUNT SET BITS IN AN INTEGER




BitsSetTable256 = [0] * 256

 

# Function to initialise the lookup table

def initialize():

     

    # To initially generate the

    # table algorithmically

    BitsSetTable256[0] = 0

    for i in range(256):

        BitsSetTable256[i] = (i & 1) + BitsSetTable256[i // 2]

 

# Function to return the count

# of set bits in n

def countSetBits(n):

    return (BitsSetTable256[n & 0xff] +

            BitsSetTable256[(n >> 8) & 0xff] +

            BitsSetTable256[(n >> 16) & 0xff] +

            BitsSetTable256[n >> 24])

 

# Driver code

 

# Initialise the lookup table

initialize()

n = 9

print(countSetBits(n))




OUTPUT:

2

CREDITS: https://www.geeksforgeeks.org/count-set-bits-in-an-integer/