Algorithms now play a very important role for the reliability and efficiency in several social systems. We study and develop new algorithmic techniques from the viewpoint of theoretical computer science. In particular, we deal with several problems related to “graphs” and “combinatorial reconfiguration.”

1. A graph consists of a set of vertices and a set of edges, each of which joins a pair of vertices. Graphs can be used to model many practical problems: For example, modeling a computer network by a graph, we can formulate the problem of finding routes of data on the network (see Fig. 1). As another example, the scheduling problem can be formulated as the graph coloring problem.

2. In combinatorial reconfiguration, we are asked to transform the current configuration into a desired one by step-by-step operations. The 15-puzzle is one of such problems (see Fig. 2), and there are many applications such as changing frequency assignments, monitoring systems, and so on.

Students in our laboratory can select research topics according to their own interests. We study algorithms from the theoretical viewpoint, but we sometimes implement developed algorithms to evaluate them from the practical viewpoint.