c++ Is there STL algorithm to check if the range is strictly sorted?

Question

By "strictly" I mean "without equivalent elements".

is_sorted(v.begin(), v.end(), std::less<>()) 

doesn't meet my goal because it returns true for ranges like 1,2,2,4,5.

is_sorted(v.begin(), v.end(), std::less_equal<>()) 

would work according to the implementation given here, but unfortunately is_sorted requires Compare predicate to be strict ordering (Compare(a,a) must be false), and std::less_equal certainly isn't.

So should I write my own loop for this purpose?

Answer 1

You can also make use of unique. It will return end of list if vector is unique.

bool is_strict_sorted(vector <int> a) {
    return is_sorted(a.begin(), a.end()) && unique(a.begin(), a.end()) == a.end();
}