boost::algorithm::is_sorted_until
// In header: <boost/algorithm/cxx11/is_sorted.hpp> template<typename ForwardIterator> ForwardIterator is_sorted_until(ForwardIterator first, ForwardIterator last);
Parameters:
first
The start of the sequence to be tested.
last
One past the end of the sequence
Returns:
the point in the sequence [first, last) where the elements are unordered