Reverse Bits leetcode

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).

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++, n >>= 1) {
            res = res << 1 | (n & 1);//给res的最后一位置为(n最右一位)
        }
        return res;
    }
}

//方法2
public int reverseBits(int n) {
        int res = 0;
        int[] tem = new int[32];
        for (int i = 0; i < 32; i++) {
            tem[i] = n >> i & 1;
        }
        for (int i = 31; i >= 0; i--) {
            res += tem[i] << (31 - i);
        }
        return res;
    }