Linked lists were used for expressing discrete blocks based on the procedure of bounding volume and the implicit grids of space decomposition. And an equivalent loop mode, in which the inner processing depended neither on the horizontal number nor on the vertical number of implicit grids, was obtained from the loop of all discrete blocks. Then, it depended neither on the size of the finite space of discrete mass distribution nor on the number of the discrete blocks. So, the CPU time for contact detection was in direct proportion to the number of blocks. The main results obtained from some examples and numerical tests indicate that the CPU time for contact detection is only in direct proportion to the number of blocks and that the CPU time for contact detection is less with respect to conventional methods.