leetcode 190: reverse bits (go)

// abcdefgh -> efghabcd -> ghefcdab -> hgfedcba
func reverseBits(n uint32) uint32 {
	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
}