矩阵和行列式

struct Determinant {
    double /* ll */ z[110][110];
    int n;
};

struct Determinant {
    ll gauss() {
        ll ret = 1;
        for (int a = 1; a <= n; ++a) {
            for (int b = a + 1; b <= n; ++b) {
                while (z[b][a] != 0) {
                    ll k = z[a][a] / z[b][a];
                    for (int c = 1; c <= n; ++c)
                        z[a][c] = z[a][c] - z[b][c] * k;
                    for (int c = 1; c <= n; ++c)
                        swap(z[a][c], z[b][c]);
                    x = -x;
                }
            }
        }
        for (int a = 1; a <= n; ++a)
            ret = ret * z[a][a];
        return ret;
    }
};