use std::iter::repeat;

fn power_level(x: i32, y: i32, serial: i32) -> i32 {
    let rack_id: i32 = x + 10;
    (rack_id * y + serial) * rack_id / 100 % 10 - 5
}

fn main() {
    const SERIAL: i32 = 8141;

    let max = (1..=300-2)
        .flat_map(|x| repeat(x).zip(1..=300 - 2))
        .max_by_key(|(x, y)| {
            let mut pow = 0;
            for x in *x..=*x + 2 {
                for y in *y..=*y + 2 {
                    pow += power_level(x, y, SERIAL);
                }
            }
            pow
        })
        .expect("no maximum found");

    println!("Part 1: {},{}", max.0, max.1);

    assert_eq!(power_level(3, 5, 8), 4);
    assert_eq!(power_level(122, 79, 57), -5);
    assert_eq!(power_level(217, 196, 39), 0);
    assert_eq!(power_level(101, 153, 71), 4);
}