def check_pow_2(num: int) -> int:
    if num == 0:
        return 0

    if num & (num - 1):
        return 1;

    return -1;

switch = {
    0: "number is 0",
    1: "number is power of 2",
    -1: "number is not power of 2 nor 0"
}

case = check_pow_2(7)
print(switch[case])

import time

def count_bits_tobe_flipped(a: int, b: int) -> int:
    x = a ^ b
    counter = 0
    while x != 0:        
        if x & 1:
            counter += 1        
        x >>= 1

    return counter


# get the start time
st = time.time()

print(count_bits_tobe_flipped(63, 20))

# get the end time
et = time.time()

# get the execution time
elapsed_time = (et - st) * 1000
print('Execution time:', elapsed_time, 'milliseconds')




def count_bits_flip(a, b):
    # XOR a and b to get 1 on opposite value bit position
    c = a ^ b

    # initialise the counter for 1
    count = 0
    # count the number of 1s while there is 1 in a ^ b
    while c != 0:
        count += 1
        c &= (c-1)

    # return the count of 1s
    return count


# get the start time
st = time.time()

print(count_bits_flip(63, 20))

# get the end time
et = time.time()
elapsed_time = (et - st) * 1000
print('Execution time:', elapsed_time, 'milliseconds')