L190. Reverse Bits

Problem:

Reverse bits of a given 32 bits unsigned integer.

Example 1:

Input: 00000010100101000001111010011100
Output: 00111001011110000010100101000000
Explanation: The input binary string 00000010100101000001111010011100 represents the unsigned integer 43261596, so return 964176192 which its binary representation is 00111001011110000010100101000000.

Solution:

public int reverseBits(int n) {
    if(n == 0) return 0;
    int mask = 0;
    int result = 0;
    
    for(int i = 0; i < 32; i++){
        mask = (n >> i) & 1;
        result |= (mask << 31 - i);
    }
    return result;
}