银行管理系统c++ 用虚函数和纯虚函数写

以下是一个银行账户管理系统的代码示例，使用了虚函数和纯虚函数：

#include <iostream>
#include <string>

using namespace std;

class Account {
protected:
    string name;
    int balance;
public:
    Account(string n, int b) : name(n), balance(b) {}
    virtual void deposit(int amount) {
        balance += amount;
        cout << "Deposit " << amount << " successfully." << endl;
    }
    virtual bool withdraw(int amount) {
        if (balance >= amount) {
            balance -= amount;
            cout << "Withdraw " << amount << " successfully." << endl;
            return true;
        }
        else {
            cout << "Withdraw " << amount << " failed." << endl;
            return false;
        }
    }
    virtual void show() {
        cout << "Name: " << name << endl;
        cout << "Balance: " << balance << endl;
    }
};

class SavingAccount : public Account {
protected:
    double rate;
public:
    SavingAccount(string n, int b, double r) : Account(n, b), rate(r) {}
    virtual void deposit(int amount) {
        balance += amount;
        cout << "Deposit " << amount << " successfully." << endl;
        balance += balance * rate;
        cout << "Interest added." << endl;
    }
};

class CheckingAccount : public Account {
protected:
    int fee;
public:
    CheckingAccount(string n, int b, int f) : Account(n, b), fee(f) {}
    virtual bool withdraw(int amount) {
        if (balance >= amount + fee) {
            balance -= amount + fee;
            cout << "Withdraw " << amount << " successfully." << endl;
            cout << "Fee " << fee << " charged." << endl;
            return true;
        }
        else {
            cout << "Withdraw " << amount << " failed." << endl;
            return false;
        }
    }
};

int main() {
    Account* a1 = new SavingAccount("Tom", 1000, 0.01);
    Account* a2 = new CheckingAccount("Jerry", 500, 10);

    a1->deposit(100);
    a1->show();
    a2->withdraw(200);
    a2->show();

    delete a1;
    delete a2;
    return 0;
}

在上面的代码中，`Account` 是一个基类，`SavingAccount` 和 `CheckingAccount` 都是它的派生类。`Account` 中定义了三个虚函数 `deposit()`、`withdraw()` 和 `show()`，并且 `withdraw()` 被声明为纯虚函数。`SavingAccount` 和 `CheckingAccount` 都重写了 `deposit()` 和 `withdraw()` 函数，而 `show()` 函数继承了 `Account` 中的实现。

在 `main()` 函数中，我们创建了一个 `SavingAccount` 对象和一个 `CheckingAccount` 对象，并通过基类指针调用它们的虚函数。由于 `withdraw()` 是纯虚函数，所以我们不能创建 `Account` 对象，只能通过派生类来创建对象。