[백준/10844/Java] 쉬운 계단 수

 

 

쉬운 계단 수

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

10844번: 쉬운 계단 수

 

 

 

풀이

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;
import java.util.stream.IntStream;


public class Main {
    
    private static BigInteger[][] dp = new BigInteger[101][10];//0~9

    static {
        dp[1][0]= BigInteger.ZERO;
        IntStream.range(1,10).forEach(i ->dp[1][i] = BigInteger.ONE);


        IntStream.rangeClosed(2,100).forEach(i -> {
            IntStream.range(0,10).forEach(k -> {
                switch (k) {
                    case 0 -> dp[i][k] = dp[i - 1][1];//0일때와 9일때는 가능성이 1개밖에 없음
                    case 9 -> dp[i][k] = dp[i - 1][8];
                    default -> dp[i][k] = dp[i - 1][k - 1].add(dp[i - 1][k + 1]);
                }
            });
        });
        
    }


    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        final int i = Integer.parseInt(br.readLine());
        BigInteger result = BigInteger.ZERO;
        for(int k =0; k<10; k++){
            result = result.add(dp[i][k]);
        }
        System.out.println(result.remainder(BigInteger.valueOf(1000000000)));
    }

}