I ran the unoptimized version of the code into ChatGPT and he was able to optimize it similarly to OPs solutions.

I was quite impressed, here is the ChatGPT version:

fn run(s: &[char], window_size: usize) -> usize { let mut unique_chars = 0; for i in 0..window_size { unique_chars |= 1 << (s[i] as u32 - 'a' as u32); } if unique_chars.count_ones() as usize == window_size { return window_size; }

    for i in 1..s.len() - window_size {
        let prev = s[i - 1] as u32 - 'a' as u32;
        let next = s[i + window_size - 1] as u32 - 'a' as u32;
        unique_chars ^= 1 << prev;
        unique_chars |= 1 << next;
        if unique_chars.count_ones() as usize == window_size {
            return i + window_size;
        }
    }

    panic!("No unique window found");

}

//NOTE: my prompt was the make the code O(N)