c++实现有一个交通工具类vehicle，将它作为基类派生小车类car，卡车类trunk和轮船类船，定义这些类并定义一个虚函数用来显示各类的信息。- 小车输出型号 - 卡车输出耗油量 - 轮船输出吨位 输入格式 标记（1->小车，2->卡车，3->轮船） 输出格式 输出信息

以下是 C++ 实现：

#include <iostream>
using namespace std;

class Vehicle {
public:
    virtual void showInfo() {
        cout << "This is a vehicle." << endl;
    }
};

class Car : public Vehicle {
public:
    void showInfo() {
        cout << "This is a car. Model: xxx." << endl;
    }
};

class Trunk : public Vehicle {
public:
    void showInfo() {
        cout << "This is a trunk. Fuel consumption: xxx." << endl;
    }
};

class Ship : public Vehicle {
public:
    void showInfo() {
        cout << "This is a ship. Tonnage: xxx." << endl;
    }
};

int main() {
    int type;
    cin >> type;
    Vehicle *v;
    switch (type) {
        case 1:
            v = new Car();
            break;
        case 2:
            v = new Trunk();
            break;
        case 3:
            v = new Ship();
            break;
        default:
            cout << "Invalid type." << endl;
            return 0;
    }
    v->showInfo();
    delete v;
    return 0;
}

输入一个标记，根据标记创建相应的对象，并调用虚函数 `showInfo()` 显示信息。