Defined in header <algorithm> template< class RandomIt >
void stable_sort( RandomIt first, RandomIt last ); (1) template< class RandomIt, class Compare >
void stable_sort( RandomIt first, RandomIt last, Compare comp ); (2)
Sorts the elements in the range [first, last) in ascending order. The order of equal elements is guaranteed to be preserved. The first version uses operator< to compare the elements, the second version uses the given comparison functi