How to remove duplicate nodes from generated path and segments inbetween?

I really need help on this. Been at it for a week.

I have a randomly generated path between nodes 1 to 25.

Initial generation: 1 6 7 2 1 6 7 8 9 4 3 2 1 6 7 12 11 16 21 22 23 24 19 20 25

I want to remove all repeated segments and nodes so based on this, the final path I want is:

(1, 6, 7, 12, 11, 16, 21, 22, 23, 24, 19, 20, 25)

How should I do this? Pls help.

This is merely a sample. I need to make the code be able to sort through a path with 500 elements or so. :( Pls help. I'm desperate.