Delete Duplicated Sublists within a List in Mathematica

Question

For instance say,

list = {{1, 2}, {3, 1}, {2, 1}, {2, 1}, {1, 1}}

I would like it to instead print

{{1, 2}, {3, 1}, {2, 1},{ {1, 1}}

I have tried DeleteDuplicates[list] and that worked to no avail. Any ideas? A loop and comparing each element would work but would take to much memory as the number of sublists I have are based on (high) factorial.

Answer 1

This is what I get (Mathematica 8):

In[1]:  list = {{1, 2}, {3, 1}, {2, 1}, {2, 1}, {1, 1}};
        DeleteDuplicates[list]

Out[1]: {{1, 2}, {3, 1}, {2, 1}, {1, 1}}

Answer 2

Another command to consider is Union. When it acts on a single list, it will delete duplicates and sort the outcome.

In[1]:= Union[{{1, 2}, {3, 1}, {2, 1}, {2, 1}, {1, 1}}]
Out[1]= {{1, 1}, {1, 2}, {2, 1}, {3, 1}}