Associative containers such as sets and maps have a contains member function, which can be used instead of the "find and check end of iterator" idiom.

std::map<int, char> map {{1, 'a'}, {2, 'b'}};
map.contains(2); // true
map.contains(123); // false

std::set<int> set {1, 2, 3};
set.contains(2); // true