The “subset sum” problem asks the question whether a list of integers contains a subset of integers that, when summed, gives zero as answer. For instance, for the list [1, 4, -3, -5, 7] the answer is “yes,” as 1 + 4 - 5 = 0. However, for the list [1, 4, -3, 7] the answer is “no,” as there is no subset of integers that adds up to zero. Write a program that solves the “subset sum” problem for a list of integers. If there is a solution, print it; if not, report that there is no solution.

This is a repetition of one of the exercises of Chapter 13¹ (Lists). In that chapter I said that you have to solve the exercise recursively. However, using the itertools module, you can now solve it without recursion (though I suspect that recursion still is used within the itertools module – you, however, do not have to).