쉬운 계단 수 - 10844번

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내 코드

package com.company;

import java.io.*;
import java.util.*;

public class Main {
    static int N;

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        N = Integer.parseInt(br.readLine());

        int[][] arr = new int[101][10];
        for (int i = 1; i < 10; i++) {
            arr[1][i] = 1;
        }

        for (int i = 1; i < N; i++) {
            arr[i + 1][0] = arr[i][1] % 1000000000;
            for (int j = 1; j <= 8; j++) {
                arr[i + 1][j] = (arr[i][j - 1] + arr[i][j + 1]) % 1000000000;
            }
            arr[i + 1][9] = arr[i][8] % 1000000000;
        }

        int ans = 0;
        for (int i = 0; i < 10; i++) {
            ans += arr[N][i];
            ans %= 1000000000;
        }

        System.out.println(ans % 1000000000);
    }


}