用穷举法找出 1~100 间的质数,显示出来。分别使用 while,do-while,for 循环语句实现。 解: 源程序: 使用 while 循环语句: #include
#include void main() { int i,j,k,flag; i = 2; while(i <= 100) { flag = 1; k = sqrt(i); j = 2; while (j <= k) { if(i%j == 0) { flag = 0; break; } j++; } if (flag) cout << i << "是质数." << endl; i++; } } 使用 do…while 循环语句: #include #include void main() { int i,j,k,flag; i = 2; do{ flag = 1; k = sqrt(i); j = 2; do{ if(i%j == 0) { flag = 0;
break; } j++; }while (j <= k); if (flag) cout << i << "是质数." << endl; i++; }while(i <= 100); } 使用 for 循环语句: #include #include void main() { int i,j,k,flag; for(i = 2; i <= 100; i++) { flag = 1; k = sqrt(i); for (j = 2; j <= k; j++) { if(i%j == 0) { flag = 0; break; } } if (flag) cout << i << "是质数." << endl; } } 2-35 定义枚举类型 weekday,包括 Sunday 到 Saturday 七个元素在程序中定义 weekday 类型 的变量,对其赋值,定义整型变量,看看能否对其赋 weekday 类型的值。 解: #include enum weekday { Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday
}; void main() { int i; weekday d = Thursday; cout << "d = " << d << endl; i = d; cout << "i = " << i << endl; d = (weekday)6; cout << "d = " << d << endl; d = weekday( 4 ); cout << "d = " << d << endl; } 程序运行输出: d=4 i=4 d=6 d=4 3-7 编写函数,参数为两个 unsigned short int 型数,返回值为第一个参数除以第二个参数的 结果,数据类型为 short int;如果第二个参数为 0,则返回值为-1。在主程序中实现输入输 出。 解: 源程序: #include short int Divider(unsigned short int a, unsigned short int b) { if (b == 0) return -1; else return a/b; } typedef unsigned short int USHORT; typedef unsigned long int ULONG; int main() { USHORT one, two; short int answer; cout << "Enter two numbers.\n Number one: "; cin >> one; cout << "Number two: "; cin >> two; answer = Divider(one, two); if (answer > -1)
cout << "Answer: " << answer; else cout << "Error, can't divide by zero!"; return 0; } 程序运行输出: Enter two numbers. Number one:8 Number two:2 Answer: 4 编写函数判断一个数是否是质数,在主程序中实现输入、输出。 解: #include #include int prime(int i); //判一个数是否是质数的函数 void main() { int i; cout << "请输入一个整数:"; cin >> i; if (prime(i)) cout << i << "是质数." << endl; else cout << i << "不是质数." << endl; } int prime(int i) { int j,k,flag; flag = 1; k = sqrt(i); for (j = 2; j <= k; j++) { if(i%j == 0) { flag = 0; break; } } if (flag) return 1; else return 0; } 程序运行输出:
请输入一个整数:1151 1151 是质数. 3-10 编写函数求两个整数的最大公约数和最小公倍数。 解: 源程序: #include #include h> int fn1(int i,int j); //求最大公约数的函数 void main() { int i,j,x,y; cout << "请输入一个正整数:"; cin >> i ; cout << "请输入另一个正整数:"; cin >> j ; x = fn1(i,j); y = i * j / x; cout << i << "和" << j << "的最大公约数是:" << x << endl; cout << i << "和" << j << "的最小公倍数是:" << y << endl; } int fn1(int i, int j) { int temp; if (i < j) { temp = i; i = j; j = i; } while(j != 0) { temp = i % j; i = j; j = temp; } return i; } 程序运行输出: 请输入一个正整数:120 请输入另一个正整数:72 120 和 72 的最大公约数是:24 120 和 72 的最小公倍数是:360 在主程序中提示输入整数 n,编写函数用递归的方法求 1 + 2 + … + n 的值。
解: #include #include int fn1(int i); void main() { int i; cout << "请输入一个正整数:"; cin >> i ; cout << "从 1 累加到" < long GetPower(int x, int y); int main() { int number, power; long answer; cout << "Enter a number: "; cin >> number; cout << "To what power? "; cin >> power; answer = GetPower(number,power); cout << number << " to the " << power << "th power is " < return (x * GetPower(x,y-1)); } 程序运行输出: Enter a number: 3 To what power? 4 3 to the 4th power is 81 使用模板函数实现 Swap( x, y ),函数功能为交换 x、y 的值。 解: 源程序: #include template void swap(T &;x, T &;y) { T z; z = x; x = y; y = z; } void main() { int j = 1, k = 2; double v = 3.0, w = 4.0; cout << "j = " < class Dog { public: Dog (int initialAge = 0, int initialWeight = 5);
~Dog(); int GetAge() { return itsAge;} // inline! void SetAge (int age) { itsAge = age;} // inline! int GetWeight() { return itsWeight;} // inline! void SetWeight (int weight) { itsAge = weight;} // inline! private: int itsAge, itsWeight; }; Dog::Dog(int initialAge, int initialWeight) { itsAge = initialAge; itsWeight = initialWeight; } Dog::~Dog() //destructor, takes no action { } int main() { Dog Jack(2,10); cout << "Jack is a Dog who
is " ; cout << Jack.GetAge() << " years old and"; cout << Jack.GetWeight() << " pounds weight.\n"; Jack.SetAge(7); Jack.SetWeight(20); cout << "Now Jack is " ; cout << Jack.GetAge() << " years old and"; cout << Jack.GetWeight() << " pounds weight."; return 0; } 程序运行输出: Jack is a Dog who is 2 years old and 10 pounds weight. Now Jack is 7 years old 20 pounds weight. 4-9 设计并测试一个名为 Rectangle 的矩形类,其属性为矩形的左下角与右上角两个点的坐 标,能计算矩形的面积。 解: 源程序: #include class Rectangle { public: Rectangle (int top, int left, int bottom, int right); ~Rectangle () {} int GetTop() const { return itsTop; }
int GetLeft() const { return itsLeft; } int GetBottom() const { return itsBottom; } int GetRight() const { return itsRight; } void SetTop(int top) { itsTop = top; } void SetLeft (int left) { itsLeft = left; } void SetBottom (int bottom) { itsBottom = bottom; } void SetRight (int right) { itsRight = right; } int GetArea() const; private: int itsTop; int itsLeft; int itsBottom; int itsRight; }; Rectangle::Rectangle(int top, int left, int bottom, int right) { itsTop = top; itsLeft = left; itsBottom = bottom; itsRight = right; } int Rectangle::GetArea() const { int Width = itsRight-itsLeft; int Height = itsTop - itsBottom; return (Width * Height); } int main() { Rectangle MyRectangle (100, 20, 50, 80 ); int Area = MyRectangle.GetArea(); cout << "Area: " << Area << "\n"; return 0; } 程序运行输出: Area: 3000 Upper Left X Coordinate: 20 定义一个矩形类,有长、宽两个属性,有成员函数计算矩形的面积 解: #include class Rectangle { public: Rectangle(float len, float width)
{ Length = len; Width = width; } ~Rectangle(){}; float GetArea() { return Length * Width; } float GetLength() { return Length; } float GetWidth() { return Width; } private: float Length; float Width; }; void main() { float length, width; cout << "请输入矩形的长度:"; cin >> length; cout << "请输入矩形的宽度:"; cin >> width; Rectangle r(length, width); cout << "长为" << length << "宽为" << width << "的矩形的面积为:" <