[BOJ] 백준 10884 쉬운 계단 수

[문제]

https://www.acmicpc.net/problem/10844

 

 

[소스 코드]

import java.io.*;
import java.util.*;
public class Main {
    public static void main(String[] args) throws IOException {
    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	int n = Integer.parseInt(br.readLine());
    	long[][] dp = new long[101][10];
    	for(int i=1;i<=9;i++) {
    		dp[1][i] = 1;
    	}
    	long result = 0;
    	for(int i=2;i<=100;i++) {
    		for(int k=0;k<=9;k++) {
    			if(k!=0) dp[i][k] += dp[i-1][k-1];
    			if(k!=9) dp[i][k] += dp[i-1][k+1];
    			dp[i][k] %= 1000000000;
    		}
    	}
    	for(int i=0;i<=9;i++) {
    		result += dp[n][i];
    	}
    	result %= 1000000000;
    	System.out.println(result);
    }
}