N-fold partition of an array with equal sum in each partition

Question

Given an array of integers a, two numbers N and M, return N group of integers from a such that each group su

Answer 1

this appears to be a variation of the subset sum problem. as this problem is np-complete, there will be no efficient algorithm without further constraints.

note that it is already hard to find a single subset of the original set whose elements would sum up to M.