This is one of the basic functionalites of the unique function, just do something like this:
A = [1 0 0 0 0
0 1 0 0 1
0 0 1 0 0
0 0 0 1 0
0 1 0 0 1];
[C,ia,ic] = unique(A,'rows');
ic
ic =
4
3
2
1
3
The ic vector is saying for which group each row belongs