nth_element

mismatch

template <class InIter1, class InIter2>    pair<InIter1, InIter2> mismatch(InIter1 start1, InIter1 end1,                                     InIter2 start2); template <class InIter1, class InIter2, class BinPred>     pair<InIter1, InIter2> mismatch(InIter1 start1, InIter1 end1,                                     InIter2 start2, BinPred pfn);

The mismatch( ) algorithm finds the first mismatch between the elements
in two sequences. Iterators to the two elements are returned. If no mismatch is found, then the iterators end1 and start2 + (end1 – start1) are returned.

The second form allows you to specify a binary predicate that determines when one element is equal to another.

The pair template class contains two data members called first and second, which hold the pair of values.