#include <cassert>
#include <initializer_list>
#include <iostream>
#include <stdexcept>
#include <utility>
#include <vector>

class Scores {
    std::vector<int> values_;
public:
    explicit Scores(std::initializer_list<int> values) {
        replace(std::vector<int>(values));
    }
    Scores(const Scores&) = default;

    void swap(Scores& other) noexcept {
        values_.swap(other.values_);
    }
    Scores& operator=(const Scores& other) {
        Scores temporary(other);
        swap(temporary);
        return *this;
    }
    void replace(std::vector<int> candidate) {
        for (int value : candidate) {
            if (value < 0) {
                throw std::invalid_argument("negative score");
            }
        }
        values_.swap(candidate);
    }
    const std::vector<int>& values() const noexcept {
        return values_;
    }
};

int main() {
    Scores scores{10, 20};
    const auto before = scores.values();
    bool rejected = false;
    try {
        scores.replace({30, -1});
    } catch (const std::invalid_argument&) {
        rejected = true;
    }
    assert(rejected);
    assert(scores.values() == before);

    Scores replacement{40, 50};
    scores = replacement;
    assert(scores.values() == replacement.values());
    const Scores& same = scores;
    scores = same;
    assert((scores.values() == std::vector<int>{40, 50}));
    scores.replace({60});
    assert((scores.values() == std::vector<int>{60}));
    static_assert(noexcept(scores.swap(replacement)),
                  "commit must not throw");
    std::cout << scores.values().front() << '\n';
}