Computational Complexity of Finding Subgroups of a Given Order

We study the problem of finding a subgroup of a given order in a finite group, where the group is represented by its Cayley table. We establish that this problem is NP-hard in the general case by providing a reduction from the Hamiltonian Cycle problem. Additionally, we analyze the complexity of the problem in the special case of abelian groups and present a linear-time algorithm for finding a subgroup of a given order when the input is given in the form of a Cayley table. To the best of our knowledge, no prior work has addressed the complexity of this problem under the Cayley table representation. Our results also provide insight into the computational difficulty of finding subgroup across different ways of groups representations.