쉬운 계단 수

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

10844번: 쉬운 계단 수

 

// 코드

import java.util.*;
import java.io.*;
 
public class Main{  
  
  // main
  public static void main(String[] args) throws Exception {
    
    long mod = 1000000000;
    
    BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); 
    int N = Integer.parseInt(br.readLine());
    long[][] dp = new long[N+1][10];
    
    for(int i=1; i<10; i++) {
      dp[1][i] = 1;
    }
    
    for(int i=2; i<=N; i++) {
      for(int j=0; j<10; j++) {
        
        if(j == 0) {
          dp[i][0] = dp[i-1][1] % mod;
        } else if(j == 9) {
          dp[i][9] = dp[i-1][8] % mod;
        } else {
          dp[i][j] = (dp[i-1][j-1] + dp[i-1][j+1]) % mod;
        }
        
      }
    }
    
    long sum = 0;
    for(int i=0; i<10; i++) {
      sum += dp[N][i];
    }
    
    bw.write(String.valueOf((sum%mod)));
    br.close();
    bw.flush();
    bw.close();
  }
}

 

// 접근법

https://st-lab.tistory.com/134

[백준] 10844번 : 쉬운 계단 수 - JAVA [자바]