lexicographical_compare

inplace_merge

template <class BiIter>    void inplace_merge(BiIter start, BiIter mid, BiIter end);template <class BiIter, class Comp>     void inplace_merge(BiIter start, BiIter mid, BiIter end,                        Comp cmpfn); 

Within a single sequence, the inplace_merge( ) algorithm merges the range defined by start and mid with the range defined by mid and end. Both ranges must be sorted in increasing order. After executing, the resulting sequence is sorted in increasing order.

The second form allows you to specify a comparison function that determines when one element is less than another.