设计一个时间类time，可以设置时间并 进行时间的加减运算，在其中添加友元函数以完成时间的输出，最后编写主函数测试。.

设计一个名为`Time`的时间类，首先需要包含小时、分钟和秒作为成员变量。我们可以使用结构体或类来实现这个功能，这里假设我们使用类：

#include <iostream>

class Time {
private:
    int hours;
    int minutes;
    int seconds;

public:
    // 构造函数初始化时间和友元函数声明
    Time(int h = 0, int m = 0, int s = 0) : hours(h), minutes(m), seconds(s) {}

    // 友元函数用于设置时间
    friend void setTime(Time &t, int h, int m, int s);

    // 友元函数用于获取时间字符串表示
    friend std::string getTimeString(const Time &t);

    // 时间的加减运算
    Time operator+(const Time &other) const;
    Time operator-(const Time &other) const;

    // 设置时间
    void setHours(int hours) { this->hours = hours; }
    void setMinutes(int minutes) { this->minutes = minutes; }
    void setSeconds(int seconds) { this->seconds = seconds; }

    // 获取当前时间
    int getHours() const { return hours; }
    int getMinutes() const { return minutes; }
    int getSeconds() const { return seconds; }
};

// 实现友元函数
void setTime(Time &t, int h, int m, int s) {
    t.hours = h;
    t.minutes = m;
    t.seconds = s;
}

std::string getTimeString(const Time &t) {
    return std::to_string(t.getHours()) + ":" + std::to_string(t.getMinutes()) + ":" + std::to_string(t.getSeconds());
}

// 时间的加减运算实现
Time Time::operator+(const Time &other) const {
    int total_hours = hours + other.hours;
    int total_minutes = minutes + other.minutes;
    int total_seconds = seconds + other.seconds;

    while (total_minutes >= 60) {
        total_hours += total_minutes / 60;
        total_minutes %= 60;
    }
    while (total_seconds >= 60) {
        total_minutes += total_seconds / 60;
        total_seconds %= 60;
    }

    return Time(total_hours, total_minutes, total_seconds);
}

Time Time::operator-(const Time &other) const {
    int result_hours = hours - other.hours;
    int result_minutes = minutes - other.minutes;
    int result_seconds = seconds - other.seconds;

    if (result_seconds < 0) {
        result_minutes--;
        result_seconds += 60;
    }
    if (result_minutes < 0 && result_hours == 0) {
        result_hours--;
        result_minutes += 60;
    }

    return Time(result_hours, result_minutes, result_seconds);
}

int main() {
    Time time1(10, 30, 45);
    Time time2(2, 15, 0);

    std::cout << "Time 1: " << getTimeString(time1) << std::endl;
    std::cout << "Time 2: " << getTimeString(time2) << std::endl;

    Time combined_time = time1 + time2;
    std::cout << "Combined time: " << getTimeString(combined_time) << std::endl;

    Time difference = time1 - time2;
    std::cout << "Difference: " << getTimeString(difference) << std::endl;

    return 0;
}

在这个例子中，`Time`类包含了基本的时间操作，如设置和获取小时、分钟和秒，并提供了友元函数以方便输出时间和进行加减运算。在`main`函数中，我们创建了两个`Time`对象并进行了简单的操作演示。