Reverse Bits

Reverse bits of a given 32 bits unsigned integer.

For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as00111001011110000010100101000000).

Follow up:
If this function is called many times, how would you optimize it?

int型整数对应二进制数移位操作，代码如下：

public class Solution {
    // you need treat n as an unsigned value
    public int reverseBits(int n) {
        int re = 0;
        int bit = 0;
        for(int i=0;i<32;i++) {
            bit = n&1;//取出n对应二进制数的最低位
            re = re|(bit<<31-i);
            n = n>>1;
        }
        return re;
        
    }
}

当然也可以这样写：

public class Solution {
    // you need treat n as an unsigned value
    public int reverseBits(int n) {
 
        return Integer.reverse(n);
        
    }
}