Solution2.java

class Solution {
    public int dieSimulator(int n, int[] rollMax) {
        int[][][] f = new int[n + 1][7][16];
        for (int j = 1; j <= 6; ++j) {
            f[1][j][1] = 1;
        }
        final int mod = (int) 1e9 + 7;
        for (int i = 2; i <= n; ++i) {
            for (int j = 1; j <= 6; ++j) {
                for (int x = 1; x <= rollMax[j - 1]; ++x) {
                    for (int k = 1; k <= 6; ++k) {
                        if (k != j) {
                            f[i][k][1] = (f[i][k][1] + f[i - 1][j][x]) % mod;
                        } else if (x + 1 <= rollMax[j - 1]) {
                            f[i][j][x + 1] = (f[i][j][x + 1] + f[i - 1][j][x]) % mod;
                        }
                    }
                }
            }
        }
        int ans = 0;
        for (int j = 1; j <= 6; ++j) {
            for (int x = 1; x <= rollMax[j - 1]; ++x) {
                ans = (ans + f[n][j][x]) % mod;
            }
        }
        return ans;
    }
}