题解 | 数楼梯

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        int count = in.nextInt();
        if(count==0){
            System.out.println(0);
            return;
        }else if(count==1){
            System.out.println(1);
            return;
        }
        long[] dp = new long[count];
        dp[0] = 1;
        dp[1] = 2;
        for(int i = 2; i < count; i++){
            dp[i] = (dp[i-1] + dp[i-2])%998244353;
        }
        long res = dp[count-1];
        System.out.println(res);
    }
}