190_reverse_bits.java

public class Solution {
    // you need treat n as an unsigned value
    public int reverseBits(int n) {
        ArrayList<Integer> arr = new ArrayList<>();
        while (n != 0) {
            arr.add(n % 2);
            n = n >>> 1;
        }
        for (int i = arr.size(); i < 32; i++) {
            arr.add(0);
        }
        long ans = 0;
        for (int i = 0; i < arr.size(); i++) {
            ans = ans * 2 + arr.get(i);
        }
        return (int) ans;
    }
}

/**
 * This is my personal record of solving Leetcode Problems. 
 * If you have any questions, please discuss them in [Issues](https://github.com/mengxinayan/leetcode/issues).
 * Copyright (C) 2020-2022  mengxinayan
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */