use std::{
    fs::File,
    io::{BufReader, Read}, collections::HashSet,
};


fn main() -> () {
    let input = File::open("input.txt").unwrap();
    let buf = BufReader::new(input);

    let window_size = 14; // lmao the ONLY change

    let mut chars_iter = buf.bytes();
    let mut window = vec![0u8; window_size]; // never mind I had forgotten this bit
    let mut dup_check = HashSet::<u8>::with_capacity(4);
    let mut cursor = window_size - 1;
    // initialise buffer
    for i in 0..window_size - 1 {
        window[i] = chars_iter.next().unwrap().unwrap();
    }
    // find non-duplicate window
    let pos = chars_iter.position(|byte| {
        let byte = byte.unwrap();
        window[cursor] = byte;
        cursor = (cursor + 1) % window_size;

        dup_check.clear();
        dup_check.extend(window.iter());
        dup_check.len() == window_size
    }).unwrap();

    let pos = pos + window_size; // account for buffer initialisation

    println!("{}", pos);
}