C - 1111gal password

https://atcoder.jp/contests/abc242/submissions/29886113

AtCoder/ABC242/C/C.cpp

@@ -0,0 +1,38 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int mod = 998244353;
+
+int n;
+long long f[1000005][10], ans;
+
+int main() {
+    cin >> n;
+    if (n == 1) {
+        cout << 9 << endl;
+        exit(0);
+    }
+    for (int i = 1; i <= 9; i++) {
+        f[1][i] = 1;
+    }
+    for (int i = 2; i <= n; i++) {
+        for (int j = 1; j <= 9; j++) {
+            f[i][j] = f[i - 1][j];
+            if (j > 1) {
+                f[i][j] += f[i - 1][j - 1];
+            }
+            if (j < 9) {
+                f[i][j] += f[i - 1][j + 1];
+            }
+            f[i][j] %= mod;
+        }
+    }
+    for (int i = 0; i <= 9; i++) {
+        ans += f[n][i];
+    }
+    cout << ans % mod << endl;
+    return 0;
+}