template<class InIt1, class InIt2>
bool lexicographical_compare(InIt1 first1, InIt1 last1,
InIt2 first2, InIt2 last2);
template<class InIt1, class InIt2, class Pred>
bool lexicographical_compare(InIt1 first1, InIt1 last1,
InIt2 first2, InIt2 last2, Pred pr);The first template function determines K, the number of elements to compare as the smaller of last1 - first1 and
last2 - first2. It then determines the lowest value of N in the range [0, K) for which *(first1 + N) and
*(first2 + N) do not have equivalent ordering. If no such value exists, the function returns true only if K < (last2
- first2). Otherwise, it returns true only if *(first1 + N) < *(first2 + N). Thus, the function returns true
only if the sequence designated by iterators in the range [first1, last1) is lexicographically less than the other
sequence.
The function evaluates the ordering predicate X < Y at most 2 * K times.
The second template function behaves the same, except that it replaces operator<(X, Y) with pr(X, Y).