20_October.cpp

class Solution
{
public:
    int getSum(int x, int y, int z)
    {
        int mod = (int)(1e9 + 7);
        long long exactsum[x + 1][y + 1][z + 1];
        long long exactnum[x + 1][y + 1][z + 1];
        memset(exactnum, 0, sizeof exactnum);
        memset(exactsum, 0, sizeof exactsum);
        long long ans = 0;
        exactnum[0][0][0] = 1;
        for (int i = 0; i <= x; ++i)
        {
            for (int j = 0; j <= y; ++j)
            {
                for (int k = 0; k <= z; ++k)
                {
                    if (i > 0)
                    {
                        exactsum[i][j][k] += (exactsum[i - 1][j][k] * 10 +
                                              4 * exactnum[i - 1][j][k]) %
                                             mod;
                        exactnum[i][j][k] += exactnum[i - 1][j][k] % mod;
                    }
                    if (j > 0)
                    {
                        exactsum[i][j][k] += (exactsum[i][j - 1][k] * 10 +
                                              5 * exactnum[i][j - 1][k]) %
                                             mod;
                        exactnum[i][j][k] += exactnum[i][j - 1][k] % mod;
                    }
                    if (k > 0)
                    {
                        exactsum[i][j][k] += (exactsum[i][j][k - 1] * 10 +
                                              6 * exactnum[i][j][k - 1]) %
                                             mod;
                        exactnum[i][j][k] += exactnum[i][j][k - 1] % mod;
                    }
                    ans += exactsum[i][j][k] % mod;
                    ans %= mod;
                }
            }
        }
        return (int)ans;
    }
};