---

export module MatMod;

export constexpr int SZ = 5;

export void mat_add(const int A[][SZ],
                    const int B[][SZ],
                    int C[][SZ])
{
    for (int i = 0; i < SZ; i++)
        for (int j = 0; j < SZ; j++)
            C[i][j] = A[i][j] + B[i][j];
}

export void mat_mul(const int A[][SZ],
                    const int B[][SZ],
                    int C[][SZ])
{
    for (int i = 0; i < SZ; i++)
        for (int j = 0; j < SZ; j++)
        {
            C[i][j] = 0;

            for (int k = 0; k < SZ; k++)
                C[i][j] = C[i][j] + A[i][k] * B[k][j];
        }
}

int det_rec(const int A[][SZ], int n)
{
    if (n == 1)
        return A[0][0];

    int s = 0;

    for (int k = 0; k < n; k++)
    {
        int B[SZ][SZ] = {};
        int bi = 0;

        for (int i = 1; i < n; i++)
        {
            int bj = 0;

            for (int j = 0; j < n; j++)
            {
                if (j != k)
                {
                    B[bi][bj] = A[i][j];
                    bj++;
                }
            }

            bi++;
        }

        if (k % 2 == 0)
            s = s + A[0][k] * det_rec(B, n - 1);
        else
            s = s - A[0][k] * det_rec(B, n - 1);
    }

    return s;
}

export int mat_det(const int A[][SZ])
{
    return det_rec(A, SZ);
}