/**
* Swaps odd and even bits in a 32-bit unsigned integer.
* For example, bit 0 and bit 1 are swapped, bit 2 and bit 3 are swapped, etc.
*/
function swapsOddAndEvenBits(n) {
// Mask to isolate odd bits: binary 101010... (hex: 0xAAAAAAAA)
const oddBits = n & 0xAAAAAAAA;
// Mask to isolate even bits: binary 010101... (hex: 0x55555555)
const evenBits = n & 0x55555555;
console.log(`oddBits: ${toBitString(oddBits, 8)}`);
console.log(`evenBits: ${toBitString(evenBits, 8)}`);
// Shift odd bits right to move them to even positions
const shiftedOddBits = oddBits >>> 1;
// Shift even bits left to move them to odd positions
const shiftedEvenBits = evenBits << 1;
console.log(`oddBits Right-shift: ${toBitString(shiftedOddBits, 8)}`);
console.log(`evenBits Left-shift: ${toBitString(shiftedEvenBits, 8)}`);
// Combine the shifted bits
return shiftedOddBits | shiftedEvenBits;
}
/**
* Converts a number to a binary string with fixed width.
* Pads with leading zeros to match the desired bit width.
*/
function toBitString(n, width) {
return (n >>> 0).toString(2).padStart(width, '0').slice(-width);
}
const n = 90;
console.log(`Input: ${toBitString(n, 8)}`);
const result = swapsOddAndEvenBits(n);
console.log(`Result: ${toBitString(result, 8)}`);
/*
run:
Input: 01011010
oddBits: 00001010
evenBits: 01010000
oddBits Right-shift: 00000101
evenBits Left-shift: 10100000
Result: 10100101
*/
