Nice kata, just a small hint for people who are getting timeouts:
A simple depth first search of breadth first search won't work. Timeout tests are designed to eliminate them.

The question is a bit vague about the "entire pair is earlier" part. As I understand a pair is earlier than another one if the indice of the element at right is smaller. Thus the answer to [10, 5, 2, 3, 7, 5] is [3, 7] instead of [5, 5] because 7 comes before the second 5. The question should be updated for a clarification.