public static long countArray(int n, int k, int x) { long mode = 1000000000 + 7; long[][] dp = new long[n + 1][2]; if (n == 2) { if (x == 1) return 0; else return 1; } if (x != 1) { dp[2][0] = 1; dp[2][1] = k - 2; } else { dp[2][0] = 0; dp[2][1] = k - 1; } for (int i = 3; i <= n; i++) { dp[i][0] = dp[i - 1][1] % mode; dp[i][1] = (dp[i - 1][1] * (k - 2) + dp[i - 1][0] * (k - 1)) % mode; }

    return dp[n][0];
}