Group centre and group median of a network

The absolute centre and median of a network can be computed in polynomial time. The authors use a partition of the nodes to define group centre and group median of the network. These ideas can be used to unify the concepts of absolute centre and median. The authors give polynomially bounded algorithms to identify group centre and group median of a network. It may be observed that the introduction of partitions in some other combinatorial optimization problems, e.g. the assignment problem, changes the polynomial nature of the problem.