用C++编写一个程序，有一个汽车类vehicle，它具有一个需要传递参数的构造函数，类中的数据成员：车轮个数wheels和车重weight放在保护段中；小车类car是它的私有派生类，其中包含载人数passenger_load；卡车类truck是vehicle的私有派生类，其中包含载人数passenger_load和载重量payload和一个求载率的函数efficiency()（假设用 payload/( payload + weight)计算）。每个类都有相关数据的输出方法，并设计主函数测试。

没问题，下面是符合要求的 C++ 代码：

#include<iostream>
using namespace std;

class Vehicle{
protected:
    int wheels, weight;
public:
    Vehicle(int w, int wei){
        wheels = w;
        weight = wei;
    }
    void show(){
        cout << "Wheels: " << wheels << endl;
        cout << "Weight: " << weight << endl;
    }
};

class Car : private Vehicle{
private:
    int passenger_load;
public:
    Car(int w, int wei, int pl) : Vehicle(w,wei){
        passenger_load = pl;
    }
    void show(){
        Vehicle::show();
        cout << "Passenger load: " << passenger_load << endl;
    }
};

class Truck : private Vehicle{
private:
    int passenger_load, payload;
public:
    Truck(int w, int wei, int pl, int pay) : Vehicle(w, wei){
        passenger_load = pl;
        payload = pay;
    }
    float efficiency(){
        return ((float)payload/(payload + weight));
    }
    void show(){
        Vehicle::show();
        cout << "Passenger load: " << passenger_load << endl;
        cout << "Payload: " << payload << endl;
    }
};

int main(){
    Vehicle v(4, 1000);
    Car c(4, 800, 5);
    Truck t(8, 5000, 2, 1000);
    v.show();
    cout << "----------------------------\n";
    c.show();
    cout << "----------------------------\n";
    t.show();
    cout << "Efficiency: " << t.efficiency()<< endl;
    return 0;
}

希望这段代码能够解决您的问题，如还有任何问题或疑问，欢迎随时向我提问哦。