///个人银行账户管理程序
#include<iostream>
#include<cmath>
using namespace std;

class SavingsAccount {
private:
	int id;					//账号
	double balance;			//余额
	double rate;			//存款的年利率
	int lastDate;			//上次变更的日期
	double accumulation;	//余额按日累加之和
	//记录一笔账，date为日期， amount为金额
	void record(int date, double amount);
	//获得到指定为止的存款按日累计值
	double accumulate(int date) const {
		return accumulation + balance * (date - lastDate);
	}
public:
	//构造函数
	SavingsAccount(int date, int id, double rate);
	int getId() { return id; }
	double getBalance() { return balance; }
	double getRate() { return rate; }
	void deposit(int date, double amount);		//存入现金
	void withdraw(int date, double amount);		//取出现金

	//结算利息，每年1月1日调用该函数
	void settle(int date);
	//显示账户信息
	void show();
};

void SavingsAccount::record(int date, double amount)
{
	accumulation = accumulate(date);
	lastDate = date;
	amount = floor(amount * 100 + 0.5) / 100;		//保留两位小数
	balance += amount;
	cout << date << "\t#" << id << "\t#" << amount << "\t#" << balance << endl;
}

SavingsAccount::SavingsAccount(int date, int id, double rate)
	:id(id),balance(0),rate(rate),lastDate(date),accumulation(0)
{
	cout << date << "\t#" << id << "is created" << endl;
}

void SavingsAccount::deposit(int date, double amount)
{
	record(date, amount);
}

void SavingsAccount::withdraw(int date, double amount)
{
	if (amount > getBalance())
	{
		cout << "Error :not enough money" << endl;
	}
	else
		record(date, -amount);
}

void SavingsAccount::settle(int date)
{
	double interest = accumulate(date) * rate / 365;			//计算年息
	if (interest != 0)
	{
		record(date, interest);
	}
	accumulation = 0;
}

void SavingsAccount::show()
{
	cout << "-》" << id << "\tBalance: " << balance;
}


int main()
{

	//建立两个账户
	SavingsAccount sa0(1, 21325302, 0.015);
	SavingsAccount sa1(1, 58320212, 0.015);
	//几笔账目
	sa0.deposit(5, 5000);		//存入现金
	sa1.deposit(25, 10000);
	sa0.deposit(45, 5500);
	sa1.withdraw(60, 4000);
	//开户后第90天后到了银行的计息日，结算所有账户年息
	sa0.settle(90);
	sa1.settle(90);
	//输出各个账户的信息
	sa0.show();  cout << endl;
	sa1.show();  cout << endl;


	system("pause");
	return 0;
}

运行结果：