  The BGG category $\mathcal{O}$ and its generalization
$\mathcal{O}^\mathfrak{p}$ play essential roles in representation theory and
have led to far-reaching work. Some elementary problems remain open for several
decades, such as the block decomposition of category
$\mathcal{O}^\mathfrak{p}$. In this paper, we solve the problem of blocks by
applying the theory of Jantzen coefficients.
