[20251106] BOJ / G1 / 계단 수 / 한종욱

Ukj0ng/202511/06 BOJ G1 계단 수.md

@@ -0,0 +1,50 @@
+```
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    private static final BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    private static final int MOD = 1000000000;
+    private static int[][][] dp;
+    private static int N;
+    public static void main(String[] args) throws IOException {
+        init();
+        long answer = 0;
+        for (int i = 0; i < 10; i++) {
+            answer += dp[N][i][(1<<10) - 1];
+            answer %= MOD;
+        }
+
+        bw.write(answer + "\n");
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    private static void init() throws IOException {
+        N = Integer.parseInt(br.readLine());
+
+        dp = new int[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 < 9) {
+                        dp[i][j+1][k | (1<<(j+1))] += dp[i-1][j][k];
+                        dp[i][j+1][k | (1<<(j+1))] %= MOD;
+                    }
+                    if (j > 0) {
+                        dp[i][j-1][k | (1<<(j-1))] += dp[i-1][j][k];
+                        dp[i][j-1][k | (1<<(j-1))] %= MOD;
+                    }
+                }
+            }
+        }
+    }
+}
+```