K-cluster combinatorial optimization problems is NP_Hardness problem in graph clustering.

This manuscript introduces a valid strategy to prove the optimization problem is the NP_Hardness problem. First of all, K-cluster is one of the most important NP-hardness problems of combinatorial optimization problems. Secondly, a problem is hard if it cannot be solved by a feasible (polynomial time) algorithm; i.e. the hard problem cannot be solved in particular. Furthermore, the strategy of this paper is to use a technique to show the problem is NP-Hard. Finally, the problem is NP-Hard if every problem from NP can be reduced to that which is means reductions proven. [ABSTRACT FROM AUTHOR]