백준 쉬운 계단수 10844번 with Kotlin

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

10844번: 쉬운 계단 수

 

import java.io.BufferedReader
import java.io.BufferedWriter
import java.io.InputStreamReader
import java.io.OutputStreamWriter
import java.lang.StringBuilder
 
val br = BufferedReader(InputStreamReader(System.`in`))
val bw = BufferedWriter(OutputStreamWriter(System.out))
val n = readLine()!!.toInt()
val graph = Array(n+1,{IntArray(10)})
fun main()=with(br) {
    for (i in 1..9) {
        graph[1][i] = 1
    }
    val mod = 1000000000
    for (i in 2..n) {
        for (j in 0..9) {
            when (j) {
                0 -> {
                    graph[i][j] = graph[i - 1][j + 1] % mod
                }
                9 -> {
                    graph[i][j] = graph[i - 1][j - 1] % mod
                }
                else -> {
                    graph[i][j] = (graph[i - 1][j - 1] + graph[i - 1][j + 1]) % mod
                }
            }
        }
    }
    var ans = 0
//    for(i in 1 .. n){
//        for(j in 0 until 10){
//            bw.write("${graph[i][j]}")
//        }
//        bw.write("\n")
//    }
    for (i in 0 until 10) {
        ans += graph[n][i]
        ans %= mod
    }
    bw.write("$ans")
    bw.flush()
    bw.close()
}