More elegant way to check for duplicates in C++ array?

Question

I wrote this code in C++ as part of a uni task where I need to ensure that there are no duplicates within an array:

// Check for duplicate numbers in user in         


        

Answer 1

fast O(N) time and space solution return first when it hits duplicate

template 
bool containsDuplicate(vector& items) {
    return any_of(items.begin(), items.end(), [s = unordered_set{}](const auto& item) mutable {
        return !s.insert(item).second;
    });
}