190-reverse-bits

/**
 * @param {number} n - a positive integer
 * @return {number} - a positive integer
 */
var reverseBits = function(n) {
    n = ((n>>>16) | (n << 16));
    n = ( ( (n&0xff00ff00) >>> 8) | ( (n&0x00ff00ff) << 8) );
    n = ( ( (n&0xf0f0f0f0) >>> 4) | ( (n&0x0f0f0f0f) << 4) );
    n = ( ( (n&0xcccccccc) >>> 2) | ( (n&0x33333333) << 2) );
    n = ( ( (n&0xaaaaaaaa) >>> 1) | ( (n&0x55555555) << 1) );
    return n >>> 0;
};