题解 | #智能指针的使用#

#include <iostream>
#include <memory>
#include <ostream>

class Student {
private:
    int _id;
    int _age;
public:
    // Rule of Zero
    Student(int id, int age) : _id(id), _age(age) {}

    // getter
    [[nodiscard]] int getId() const {
        return _id;
    }
    [[nodiscard]] int getAge() const {
        return _age;
    }

    // 打印函数，用于输出学生的信息还有 shared_ptr 的引用计数
    static void print(std::shared_ptr<Student>& student) {
        std::cout << student->getId() << " " << student->getAge() << " "
                  << student.use_count() << std::endl;
    }
};

int main() {
    int T, N;
    std::cin >> T;

    while (T--) {
        std::cin >> N;
        std::shared_ptr<Student> sp;

        for (int i = 0; i < N; ++i) {
            std::string command;
            std::cin >> command;

            // 处理各种操作
            if (command == "new") {
                int id, age;
                std::cin >> id >> age;
                sp = std::make_shared<Student>(id, age); // 创建新的 Student 对象
            } else if (command == "copy") {
                auto new_sp = sp; // 复制 shared_ptr
                sp = new_sp;
            } else if (command == "print") {
                Student::print(sp);
            } else {
                std::cout << "usage1: new id age" << std::endl
                          << "usage2: copy" << std::endl
                          << "usage3: print" << std::endl
                          << "Please try again..." << std::endl;
                return -1;
            }
        }
    }
    return 0;
}
// 64 位输出请用 printf("%lld")