Yup, in time (and space) O(M • n), so with M = 1 million and let's say n = 1 million, it takes space 1 trillion. Given a byte per number, it takes a TB of memor

Yup, in time (and space) O(M • n), so with M = 1 million and let's say n = 1 million, it takes space 1 trillion. Given a byte per number, it takes a TB of memory, but is otherwise doable. Ps, you don't want to risk a running time of form O(Mn²).