/// It is not actually necissary or even recommended to use this code.
/// The compiler should always optimize division with constant denominators for you.
/// This code is just to help understand how the compilers optimization works.
#[inline(always)]
pub fn div10(num: u32) -> (u32, u32) {
    // Calculate num / 10
    // Note: 0.10 = 3435973837 / (1<<35)
    let quot: u32 = ((3435973837_u64 * num as u64) >> 35) as u32;

    // Calculate quot * 10
    // Note: 10x = 2x + 4(2x)
    let quot2 = quot << 1;
    let quot8 = quot2 << 2;
    let quot10 = quot2 + quot8;

    // Calculate the remainder
    // Note: rem = num - (quotient * denominator)
    let rem = num - quot10;

    return (quot, rem);
}

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

    #[test]
    fn brute_check() {
        for i in 0..=u32::MAX {
            let ans = (i / 10, i % 10);
            assert_eq!(ans, div10(i));
        }
    }
}