"""

Swap Pair

Swap odd and even bits of an integer using bitmask operations. Bit 0 is

swapped with bit 1, bit 2 with bit 3, and so on.

Reference: https://en.wikipedia.org/wiki/Bit_manipulation

Complexity:

Time: O(1)

Space: O(1)

"""

from __future__ import annotations

def swap_pair(number: int) -> int:

"""Swap every pair of adjacent bits in an integer.

Masks odd-positioned bits (0xAAAAAAAA), shifts them right by one,

masks even-positioned bits (0x55555555), shifts them left by one,

and merges the results.

Args:

number: A non-negative integer.

Returns:

The integer with each adjacent pair of bits swapped.

Examples:

>>> swap_pair(22)

41

>>> swap_pair(10)

5

"""

odd_bits = (number & int("AAAAAAAA", 16)) >> 1

even_bits = (number & int("55555555", 16)) << 1

return odd_bits | even_bits