[20250210] BOJ / G1 / 계단 수 / 신희을

Author: ShinHeeEul

ShinHeeEul/202502/10 BOJ G1 계단 수.md

@@ -0,0 +1,52 @@
+```java
+import java.util.*;
+
+import java.io.*;
+
+public class Main {
+
+    static long[][][] dp;
+    static int N;
+    static final long MOD = 1000000000L;
+
+    public static void main(String[] args) throws Exception {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+
+        N = Integer.parseInt(br.readLine());
+            if (N <= 9) {
+                System.out.println(0);
+                return;
+            }
+
+            // i는 현재 길이
+            // j는 마지막 값
+            // k는 현재 방문 값
+            dp = new long[N + 1][10][(1 << 10)];
+
+            for(int i = 1; i < 10; i++) {
+                dp[1][i][(1 << i)] = 1;
+            }
+
+            for(int i = 2; i <= N; i++) {
+                for(int j = 0; j < 10; j++) {
+                    for(int k = 0; k < (1 << 10); k++) {
+                        if(j == 0) dp[i][j][k | ( 1 << j)] += dp[i - 1][j + 1][k] %MOD;
+                        else if(j == 9) dp[i][j][k | ( 1 << j)] += dp[i-1][j - 1][k] %MOD;
+                        else dp[i][j][k | ( 1 << j)] += (dp[i-1][j-1][k] + dp[i-1][j+1][k]) %MOD;
+                    }
+                }
+            }
+
+            long sum = 0;
+
+            for(int j = 0; j < 10; j++) {
+                    sum += dp[N][j][(1<< 10) - 1] %MOD;
+            }
+
+            System.out.println(sum % MOD);
+
+    }
+
+}
+
+```