The ground-state energy of a system consisting of four identical bosons or fermions is calculated using the Yakubovsky differential equations which are formulated in configuration space. The solution is restricted to include s waves only. Spline approximation and orthogonal collocation reduce the Yakubovsky equations to a matrix equation which is solved using the Lanczos algorithm. Storage requirements are reduced by more than three orders of a magnitude by exploiting the tensor structure present in the equation. Some of the results obtained with these methods are presented. All calculations are done on a workstation. The calculated binding energies have more than five significant digits, and it is therefore expected that the exploitation of the tensor structure makes it possible to use the Yakubovsky differential equations for realistic ground-state energy calculations with a higher accuracy than is possible with other methods.