Problem109.js

// Problem 109
//
// This problem was asked by Cisco.
//
// Given an unsigned 8-bit integer, swap its even and odd bits. The 1st and 2nd bit should be swapped, the 3rd and 4th bit should be swapped, and so on.
//
// For example, 10101010 should be 01010101. 11100010 should be 11010001.
//
// Bonus: Can you do this in one line?
//
// https://dailycodingproblem.com/blog/neat-bitwise-trick/

/**
 * Returns the swapped even and odd bits
 * @param {number} num
 * @return {number}
 */
function swapBits(num) {
  // apply bitmask over all the even and odd bits
  // then shift even bitmask right by 1, and shift odd bitmask left by 1
  return ((num & 0b10101010) >> 1) | ((num & 0b01010101) << 1);
}

export default swapBits;