In this paper a novel programmable approach to execute implicit routing algorithms is presented. The proposed router is based on an associative scheme that uses the attributes of the routing algorithm and the interconnection network topology. In this approach routing algorithms are mapped (or programmed) onto a set of bit-patterns that are matched in parallel. To show the applicability of this router, we have selected oblivious and fault-tolerant routing algorithms for ten different tree interconnection network topologies; however, the proposed scheme is flexible enough to accommodate other network topologies and routing algorithms. For the studied topologies, the number of required bit-patterns is of the same order as the topology degree. The proposed organization requires only one comparison and one read delays. This in turn yields a high-speed port assignment that is comparable to single topology routers (non-flexible routers). In the context of flexible router schemes, the proposed approach not only is one of the fastest but also requires a very small amount of hardware for its implementation.