改造Set类，重载+（并集）、（-）差集、*（交集）、<<（输出）、>>（输入）和函数调用操作符（添加一个元素）

以下是改造后的Set类代码：

#include <iostream>
#include <set>
using namespace std;

class Set {
private:
    set<int> s;

public:
    Set() {}

    // 添加一个元素
    void operator()(int x) {
        s.insert(x);
    }

    // 并集
    Set operator+(const Set& other) const {
        Set res;
        set_union(s.begin(), s.end(), other.s.begin(), other.s.end(), inserter(res.s, res.s.begin()));
        return res;
    }

    // 差集
    Set operator-(const Set& other) const {
        Set res;
        set_difference(s.begin(), s.end(), other.s.begin(), other.s.end(), inserter(res.s, res.s.begin()));
        return res;
    }

    // 交集
    Set operator*(const Set& other) const {
        Set res;
        set_intersection(s.begin(), s.end(), other.s.begin(), other.s.end(), inserter(res.s, res.s.begin()));
        return res;
    }

    // 输出
    friend ostream& operator<<(ostream& os, const Set& obj) {
        os << "{";
        for (auto it = obj.s.begin(); it != obj.s.end(); ++it) {
            os << *it;
            if (next(it) != obj.s.end())
                os << ", ";
        }
        os << "}";
        return os;
    }

    // 输入
    friend istream& operator>>(istream& is, Set& obj) {
        int n;
        is >> n;
        for (int i = 0; i < n; ++i) {
            int x;
            is >> x;
            obj.s.insert(x);
        }
        return is;
    }
};

使用示例：

int main() {
    Set s1, s2;
    cout << "Enter set 1: ";
    cin >> s1;
    cout << "Enter set 2: ";
    cin >> s2;

    Set s3 = s1 + s2;
    Set s4 = s1 - s2;
    Set s5 = s1 * s2;

    cout << "Set 1: " << s1 << endl;
    cout << "Set 2: " << s2 << endl;
    cout << "Union: " << s3 << endl;
    cout << "Difference: " << s4 << endl;
    cout << "Intersection: " << s5 << endl;

    s1(10);
    cout << "After adding 10 to set 1: " << s1 << endl;

    return 0;
}