For the vector: 17 3 5 -4 1 12 -10 -1 14 7 -6 8 15 -11 2 -2 18 4 -3 0 

A partial_sort of seven elements gives: 
     -11 -10 -6 -4 -3 -2 -1 17 14 12 7 8 15 5 3 2 18 4 1 0 

A partial_sort_copy of the last ten elements gives: 
     0 1 2 3 4 5 7 8 15 18