Reverse bits of a given 32 bits unsigned integer.
For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as 00111001011110000010100101000000).
Follow up:If this function is called many times, how would you optimize it?
Related problem: Reverse Integer

一刷
有個很簡單的做法，就是從尾部開始，逐漸構造一個新的數組。注意，由于是32 bit unsigned integer, 右移用>>>，表示無符號右移

public class Solution {
    // you need treat n as an unsigned value
    public int reverseBits(int n) {
        int res = 0;
        for(int i=0; i<32; i++){
            res += n&1;
            n = n >>>1;
            if(i<31){
                res = res<<1;
            }
        }
        return res;
    }
}