代码清单3-1 计算利息的程序（版本1）
//文件名：3-1.cpp
//计算利息
#include <iostream>
#include <cmath>
using namespace std;
int main()
{
const double oneYearRate = 0.025, twoYearRate = 0.028;
double balance, interest;
int type, startDate, endDate;;
cout << "请输入存款类型（1：一年期， 2：两年期）：";
cin >> type;
cout << "请输入存款金额：";
cin >> balance;
cout << "请输入起始日期：";
cin >> startDate;
cout << "请输入终止日期：";
cin >> endDate;
if (type == 1)
interest = pow( 1 + oneYearRate, endDate - startDate) * balance - balance;
else
interest = pow( 1 + twoYearRate, endDate - startDate) * balance - balance;
cout << balance << " 元存 " << endDate - startDate << " 年共得利息 "
<< interest << "元" << endl;
return 0;
}代码清单3-2 计算利息的程序（版本2）
//文件名：3-2.cpp
//计算利息
#include <iostream>
#include <cmath>
using namespace std;
int main()
{
const double oneYearRate = 0.025, twoYearRate = 0.028;
double balance, interest, rate;
int startDate, endDate;;
char type;
cout << "请输入存款类型（O：一年期， T：两年期）：";
cin >> type;
cout << "请输入存款金额：";
cin >> balance;
cout << "请输入起始日期：";
cin >> startDate;
cout << "请输入终止日期：";
cin >> endDate;
if (type == 'O')
rate = oneYearRate;
else
rate = twoYearRate;
interest = pow( 1 + rate, endDate - startDate) * balance - balance;
cout << balance << " 元存 " << endDate - startDate << " 年共得利息 "
<< interest << "元" << endl;
return 0;
}代码清单3-3 判断闰年的程序
//文件名：3-3.cpp
//判断闰年
#include <iostream>
using namespace std;
int main()
{
int year;
bool result;
cout << "请输入所要验证的年份：";
cin >> year;
result = (year % 4 == 0 && year % 100 != 0) || year % 400 == 0;
if (result) cout << year << "是闰年" << endl;
else cout << year << "不是闰年" << endl;
return 0;
}代码清单3-4 求一元二次方程解的程序
//文件名：3-4.cpp
//求一元二次方程解
#include <iostream>
#include <cmath> //sqrt所属的库
using namespace std;
int main()
{
double a, b, c, x1, x2, dlt;
cout << "请输入3个参数：" << endl;
cout << "输入 a:"; cin >> a ;
cout << "输入 b:"; cin >> b ;
cout << "输入 c:"; cin >> c ;
if (a == 0)
if (b == 0) cout << "非法方程" << endl;
else cout << "是一元一次方程，x = " << -c / b << endl;
else {
dlt = b * b - 4 * a * c;
if (dlt > 0) { //有两个实根
x1 = (-b + sqrt(dlt)) / 2 / a;
x2 = (-b - sqrt(dlt)) / 2 / a;
cout << "x1 = " << x1 << " x2 = " << x2 << endl;
} else if (dlt == 0) // 有两个等根
cout << "x1 = x2 = " << -b / a / 2 << endl;
else cout << "无根" << endl; //无实根
}
return 0;
}代码清单3-5 判断点(x, y)是否落在以原点为圆心，r为半径的圆内的程序
//文件名：3-5.cpp
//判断点(x, y)是否落在以原点为圆心，r为半径的圆内
#include <iostream>
using namespace std;
int main()
{
double radius, x, y;
cout << "请输入圆的半径：";
cin >> radius;
cout << "请输入点的坐标：";
cin >> x >> y;
cout << "点(" << x << ", " << y << ")" << (x * x + y * y <= radius * radius ? "" : "没有")
<< "落在圆内" << endl;
return 0;
}代码清单3-6 利息计算程序
//文件名：3-6.cpp
//计算利息
#include <iostream>
#include <cmath>
using namespace std;
int main()
{
const double rate1Year = 0.025, rate2Year = 0.028, currentRate = 0.012;
double balance, interest;
int startDate, endDate, type;
cout << "请输入存款类型（1：一年期， 2：两年期， 0：活期）：";
cin >> type;
cout << "请输入存款金额：";
cin >> balance;
cout << "请输入起始日期：";
cin >> startDate;
cout << "请输入终止日期：";
cin >> endDate;
switch (type) {
case 0: interest = pow( 1 + currentRate, endDate - startDate) * balance - balance;; break;
case 1: interest = pow( 1 + rate1Year, endDate - startDate) * balance - balance; break;
case 2: interest = pow( 1 + rate2Year, endDate - startDate) * balance - balance; break;
}
cout << balance << " 元存 " << endDate - startDate << " 年共得利息 "
<< interest << "元" << endl;
return 0;
}代码清单3-7 分数转换程序
//文件名：3-7.cpp
//将百分制转换成5个等级(A、B、C、D、E)
#include <iostream>
using namespace std;
int main()
{
int score;
cout << "请输入分数:";
cin >> score;
switch(score / 10) {
case 10:
case 9: cout << "A"; break;
case 8: cout << "B"; break;
case 7: cout << "C"; break;
case 6: cout << "D"; break;
default: cout << "E";
}
cout << endl;
return 0;
}代码清单3-8 自动出题程序
//文件名：3-8.cpp
//自动出题程序
#include <cstdlib>
#include <iostream>
using namespace std;
int main()
{
int num1, num2, op, result1, result2; //num1,num2:操作数，op:运算符，
//result1,result2:结果
num1 = rand() * 10 / (RAND_MAX + 1); //生成运算数
num2 = rand() * 10 / (RAND_MAX + 1); //生成运算数
op = rand() * 4 / (RAND_MAX + 1); //生成运算符 0--+，1-- -，2--*，3-- /
switch (op) {
case 0:
cout << num1 << " + " << num2 << " =? " ;
cin >> result1;
if (num1 + num2 == result1) cout << "you are right\n";
else cout << "you are wrong\n";
break;
case 1:
cout << num1 << " - " << num2 << " =? " ;
cin >> result1;
if (num1 - num2 == result1) cout << "you are right\n";
else cout << "you are wrong\n";
break;
case 2:
cout << num1 << " * " << num2 << " =? " ;
cin >> result1;
if (num1 * num2 == result1) cout << "you are right\n";
else cout << "you are wrong\n";
break;
case 3:
cout << num1 << " / " << num2 << " =? " ;
cin >> result1;
cout << "余数为=? ";
cin >> result2;
if ((num1 / num2 == result1) && (num1 % num2 == result2))
cout << "you are right\n";
else cout << "you are wrong\n";
break;
}
return 0;
}代码清单3-9 修改后的自动出题程序
//文件名：3-9.cpp
//自动出题程序
#include <cstdlib>
#include <ctime>
#include <iostream>
using namespace std;
int main()
{
int num1, num2, op, result1, result2; //num1,num2:操作数，op:运算符，
//result1,result2:结果
srand(time(NULL)); //随机数种子初始化
num1 = rand() * 10 / (RAND_MAX + 1); //生成运算数
num2 = rand() * 10 / (RAND_MAX + 1); //生成运算数
op = rand() * 4 / (RAND_MAX + 1); //生成运算符 0--+，1-- -，2--*，3-- /
switch (op) {
case 0:
cout << num1 << " + " << num2 << " =? " ;
cin >> result1;
if (num1 + num2 == result1) cout << "you are right\n";
else cout << "you are wrong\n";
break;
case 1:
cout << num1 << " - " << num2 << " =? " ;
cin >> result1;
if (num1 - num2 == result1) cout << "you are right\n";
else cout << "you are wrong\n";
break;
case 2:
cout << num1 << " * " << num2 << " =? " ;
cin >> result1;
if (num1 * num2 == result1) cout << "you are right\n";
else cout << "you are wrong\n";
break;
case 3:
cout << num1 << " / " << num2 << " =? " ;
cin >> result1;
cout << "余数为=? ";
cin >> result2;
if ((num1 / num2 == result1) && (num1 % num2 == result2))
cout << "you are right\n";
else cout << "you are wrong\n";
break;
}
return 0;
}