atcoder_easy_order.rs

#[derive(Eq, PartialEq)]
struct Item {
    date: usize,
    cost: usize,
}

macro_rules! easy_ord {
    ($y:ident, $x:expr) => {
        impl Ord for $y {
            fn cmp(&self, other: &Self) -> std::cmp::Ordering {
                $x(self, other)
            }
        }

        impl PartialOrd for $y {
            fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
                Some(self.cmp(other))
            }
        }
    };
}

easy_ord!(Item, |x: &Item, other: &Item| {
    if x.date < other.date {
        std::cmp::Ordering::Greater
    } else if x.date > other.date {
        std::cmp::Ordering::Less
    } else {
        usize::cmp(&x.cost, &other.cost)
    }
});