AtCoder Beginner Contest 291 D

https://atcoder.jp/contests/abc291/tasks/abc291_d

単なるDPですね。
ギリギリi32で足ります。

// Flip Cards
#![allow(non_snake_case)]

const D: i32 = 998244353;

//////////////////// library ////////////////////

fn read<T: std::str::FromStr>() -> T {
    let mut line = String::new();
    std::io::stdin().read_line(&mut line).ok();
    line.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>().split_whitespace()
            .map(|e| e.parse().ok().unwrap()).collect()
}

//////////////////// process ////////////////////

type Card = (i32, i32);

fn read_input() -> Vec<Card> {
    let N: usize = read();
    let cards: Vec<Card> = (0..N).map(|_| read_vec()).
                                    map(|v| (v[0], v[1])).collect();
    cards
}

fn proceed(dp: (i32, i32), card1: Card, card2: Card) -> (i32, i32) {
    let step = |a, b, c| if a == b { 0 } else { c };
    ((step(card1.0, card2.0, dp.0) + step(card1.1, card2.0, dp.1)) % D,
     (step(card1.0, card2.1, dp.0) + step(card1.1, card2.1, dp.1)) % D)
}

fn f(cards: Vec<Card>) -> i32 {
    let mut dp = (1, 1);
    for i in 1..cards.len() {
        dp = proceed(dp, cards[i-1], cards[i])
    }
    (dp.0 + dp.1) % D
}

fn main() {
    let cards = read_input();
    println!("{}", f(cards))
}