LeetCode-Reverse Bits

Posted 2020-08-09 LiBlog

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

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

Analysis:

Shift result to left by 1 bit, get the last bit of n, put the bit onto result.

Solution:

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