帮我看看我修改后的代码有什么问题：#include<iostream> #include<string> using namespace std; class Vehicle { protected: string no; //编号 public: Vehicle(string no) { this->no = no; } virtual void display() = 0; //应收费用 }; class Car :public Vehicle { public: int num; float weight; Car(string no, int num, float weight) :Vehicle(no) { this->num = num; this->weight = weight; } void display() { cout << no << " " << num * 8 + weight + 2 << endl; } }; class Bus:public Vehicle { public: int num; Bus(string no, int num) :Vehicle(no) { this->num = num; } void display() { cout << no << " " << num*30 << endl; } }; class Truck :public Vehicle { public: float weight; Truck(string no, int weight) :Vehicle(no) { this->weight = weight; } void display() { cout << no << " " << weight* 5 << endl; } }; int main() { int t; cin >> t; int type; string no; int num; float weight; while (t--) { cin >> type >> no; if (type == 1){ cin >> num >> weight; Vehicle* pv = new Car(no,num,weight);; } else if (type == 2) { cin >> weight; Vehicle* pv = new Truck (no, weight);; } else if (type == 3) { cin >> num ; Vehicle* pv =new Bus(no,num);; } pv->display(); } return 0; }

在代码中，对象指针 `pv` 在条件语句中被定义并初始化，但是在条件语句块之外被使用。这会导致编译错误，因为在使用它时，它可能没有被初始化。要解决这个问题，可以将对象指针的定义移动到条件语句块之前。修改后的代码如下所示：

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

class Vehicle {
protected:
    string no; //编号
public:
    Vehicle(string no)
    {
        this->no = no;
    }
    virtual void display() = 0; //应收费用
};

class Car :public Vehicle {
public:
    int num;
    float weight;
    Car(string no, int num, float weight) :Vehicle(no)
    {
        this->num = num;
        this->weight = weight;
    }
    void display()
    {
        cout << no << " " << num * 8 + weight + 2 << endl;
    }
};

class Bus :public Vehicle {
public:
    int num;
    Bus(string no, int num) :Vehicle(no)
    {
        this->num = num;
    }
    void display()
    {
        cout << no << " " << num * 30 << endl;
    }
};

class Truck :public Vehicle {
public:
    float weight;
    Truck(string no, float weight) :Vehicle(no)
    {
        this->weight = weight;
    }
    void display()
    {
        cout << no << " " << weight * 5 << endl;
    }
};

int main() {
    int t;
    cin >> t;
    int type;
    string no;
    int num;
    float weight;
    while (t--)
    {
        cin >> type >> no;
        Vehicle* pv;
        if (type == 1) {
            cin >> num >> weight;
            pv = new Car(no, num, weight);
        }
        else if (type == 2) {
            cin >> weight;
            pv = new Truck(no, weight);
        }
        else if (type == 3) {
            cin >> num;
            pv = new Bus(no, num);
        }
        pv->display();
    }
    return 0;
}

另外，还有一个小错误：在 `Truck` 类中的构造函数中，`weight` 参数应该为 `float` 类型而不是 `int` 类型。已经在上面的代码中进行了修正。