Задача о рюкзаке

#include <iostream>
#include <iomanip>
#include <list>
using namespace std;
struct Thing {
    double cost;
    double weight;
    Thing(double cost, double weight) : cost(cost), weight(weight) { }
    friend bool operator==(const Thing& a, const Thing& b) {
        return a.cost == b.cost && a.weight == b.weight;
    }
};
class Backpack {
public:
    Backpack(double limit) : limit_(limit), best_(0) { }
    list<Thing> enumeration(list<Thing>& things) {
        if (things.size() > 0) check(things);
        for (auto& thing : things) {
            auto tmp = list<Thing>(things);
            tmp.remove(thing);
            enumeration(tmp);
        }
        return things_;
    }
private:
    double limit_;
    double best_;
    list<Thing> things_;
    double weight_(list<Thing>& things)const {
        auto sum = 0.0;
        for (auto& thing : things) sum += thing.weight;
        return sum;
    }
    double cost_(list<Thing>& things)const {
        auto sum = 0.0;
        for (auto& thing : things) sum += thing.cost;
        return sum;
    }
    void check(list<Thing>& things) {
        if (0 == things_.size()) {
            if (weight_(things) <= limit_) {
                things_ = things;
                best_ = cost_(things);
            }
        }
        else {
            if (weight_(things) <= limit_ && cost_(things) > best_) {
                things_ = things;
                best_ = cost_(things);
            }
        }
    }
};
list<Thing> input(unsigned quantity) {
    list<Thing> things;
    for (auto i = 0U; i < quantity; ++i) {
        cout << "Цена " << i + 1 << " предмета: ";
        double cost;
        cin >> cost;
        cout << "Вес " << i + 1 << " предмета: ";
        double weight;
        cin >> weight;
        things.emplace_back(Thing(cost, weight));
    }
    return things;
}
void show(list<Thing>& things) {
    auto weight = 0.0;
    auto cost = 0.0;
    for (auto& thing : things) {
        weight += thing.weight;
        cost += thing.cost;
        cout
            << "Вес: " << thing.weight
            << ", цена: " << thing.cost << '\n';
    }
    cout << "Общий вес: " << weight << ", сумма: " << cost << '\n';
}
int main() {
    setlocale(LC_CTYPE, "Russian");
    cout << "Введите предельный вес рюкзака: ";
    double weight;
    cin >> weight;
    Backpack backpack(weight);
    cout << "Введите количество предметов: ";
    unsigned quantity;
    cin >> quantity;
    auto things = input(quantity);
    auto result = backpack.enumeration(things);
    show(result);
    system("pause");
}