reverse_bits.py

"""
# Reverse Bits
You are given a 32-bit unsigned integer n. Your task is to reverse
the order of its bits and return the resulting integer.
----------------------
1010 >> 1   0
 101 >> 1   01
  10 >> 1   010
   1 >> 1   0101
"""""

def reverse_bits(num):
    rev = 0
    for _ in range(32): # 32 bit
        rev = (rev << 1) | (num & 1)  # left shift + add the last bit of num
        num = num >> 1
    return rev


if __name__ == '__main__':
    from utils import test
    test(reverse_bits(0b10000000000000000000000000000000), 0b00000000000000000000000000000001)
    test(reverse_bits(0b00000000000000000000000000000001), 0b10000000000000000000000000000000)
    test(reverse_bits(0b00000000000000000000000000011010), 0b01011000000000000000000000000000)
    test(reverse_bits(0b00000000000000000000000010000000), 0b00000001000000000000000000000000)
    test(reverse_bits(0b00000000000000000000000011000000), 0b00000011000000000000000000000000)
    test(reverse_bits(0b00000000000000000000000011001000), 0b00010011000000000000000000000000)
    test(reverse_bits(0b01010101010101010101010101010101), 0b10101010101010101010101010101010)

    from utils import plot_time_complexity
    plot_time_complexity(reverse_bits, lambda n: n)