題目連結: https://leetcode.com/problems/reverse-bits/

參考解法: https://leetcode.com/problems/reverse-bits/discuss/1583277/Swift-Bit-manipulation-with-explanation

func reverseBits(_ n: Int) -> Int {
    var tmp = n
    var result = 0
    for _ in 1 ... 32 {
        let val = tmp & 1
        result = result << 1 + val
        tmp = tmp >> 1
    }
    return result
}