std::set

#include <iostream>
#include <set>

int main() {
    std::set<int> s{3, 1, 2, 1, 3};
    for (int x : s) std::cout << x << ' ';
    std::cout << '\n';
    return 0;
}

#include <iostream>
#include <set>

int main() {
    std::set<std::string> s;
    s.insert("apple");
    s.insert("banana");
    s.insert("apple");
    std::cout << s.size() << " unique items\n";
    return 0;
}

#include <iostream>
#include <set>

int main() {
    std::set<int> s{1, 2};
    auto r = s.insert(2);
    std::cout << std::boolalpha << "inserted: " << r.second << '\n';
    auto r2 = s.insert(5);
    std::cout << "inserted: " << r2.second << '\n';
    return 0;
}

#include <iostream>
#include <set>

int main() {
    std::set<int> s{10, 20, 30};
    std::cout << s.count(20) << '\n';
    std::cout << s.count(99) << '\n';
    return 0;
}

#include <iostream>
#include <set>

int main() {
    std::set<std::string> s{"red", "green", "blue"};
    auto it = s.find("green");
    std::cout << (it != s.end() ? "found" : "missing") << '\n';
    return 0;
}

#include <iostream>
#include <set>

int main() {
    std::set<int> s{1, 2, 3, 4};
    s.erase(3);
    for (int x : s) std::cout << x << ' ';
    std::cout << '\n';
    return 0;
}

#include <iostream>
#include <set>

int main() {
    std::set<int> s{50, 10, 40, 20, 30};
    for (int x : s) std::cout << x << ' ';
    std::cout << '\n';
    return 0;
}

#include <iostream>
#include <set>
#include <vector>

int main() {
    std::vector<int> v{4, 2, 4, 1, 2, 3, 1};
    std::set<int> unique(v.begin(), v.end());
    for (int x : unique) std::cout << x << ' ';
    std::cout << '\n';
    return 0;
}

#include <iostream>
#include <set>

int main() {
    std::set<int> s{10, 20, 30, 40, 50};
    auto lo = s.lower_bound(20);
    auto hi = s.upper_bound(40);
    for (auto it = lo; it != hi; ++it) std::cout << *it << ' ';
    std::cout << '\n';
    return 0;
}

#include <iostream>
#include <set>

int main() {
    std::set<int> s{1, 2, 3};
    std::cout << s.size() << '\n';
    s.clear();
    std::cout << std::boolalpha << s.empty() << '\n';
    return 0;
}

#include <iostream>
#include <set>

int main() {
    std::set<int> s{1, 2, 3};
    int more[] = {3, 4, 5};
    s.insert(more, more + 3);
    for (int x : s) std::cout << x << ' ';
    std::cout << '\n';
    return 0;
}