I'm having trouble coming up with the most efficient algorithm to remove duplicates from List<List<int>>, for example (I know this looks like a list of int[], but just doing it that way for visual purposes:

my_list[0]= {1, 2, 3};
my_list[1]= {1, 2, 3};
my_list[2]= {9, 10, 11};
my_list[3]= {1, 2, 3};

So the output would just be

new_list[0]= {1, 2, 3};
new_list[1]= {9, 10, 11};

Let me know if you have any ideas. I would really appreciate it.