reverse_bits.rs

// Time : O(logn) = O(32)
// Space: O(1)

pub struct Solution1 {}
impl Solution1 {
    pub fn reverse_bits(mut n: u32) -> u32 {
        let mut result: u32 = 0;
        (0..32).for_each(|_| {
            result <<= 1;
            result |= n & 1;
            n >>= 1;
        });
        result
    }
}

pub struct Solution2 {}
impl Solution2 {
    pub fn reverse_bits(mut n: u32) -> u32 {
        let mut result: u32 = 0;
        for _ in 0..32 {
            result <<= 1;
            result |= n & 1;
            n >>= 1;
        }
        result
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_reverse_bits() {
        assert_eq!(
            Solution1::reverse_bits(
                u32::from_str_radix("00000010100101000001111010011100", 2).unwrap()
            ),
            u32::from_str_radix("00111001011110000010100101000000", 2).unwrap()
        );
        assert_eq!(
            Solution1::reverse_bits(
                u32::from_str_radix("11111111111111111111111111111101", 2).unwrap()
            ),
            u32::from_str_radix("10111111111111111111111111111111", 2).unwrap()
        );

        assert_eq!(
            Solution2::reverse_bits(
                u32::from_str_radix("00000010100101000001111010011100", 2).unwrap()
            ),
            u32::from_str_radix("00111001011110000010100101000000", 2).unwrap()
        );
        assert_eq!(
            Solution2::reverse_bits(
                u32::from_str_radix("11111111111111111111111111111101", 2).unwrap()
            ),
            u32::from_str_radix("10111111111111111111111111111111", 2).unwrap()
        );
    }
}