程序设计部分答案

//2-26 #include<iostream> using namespace std; int main() { char c;//设置一个名叫c的字符型变量do//大括号内do while 循环体，即循环的内容{ cout<<"现在正在下雨吗？(Y/N)"; cin>>c; cout<<endl;//输出一个回车if ((c=='Y')||(c=='y')) cout<<"现在正在下雨"<<endl; if ((c=='N')||(c=='n')) cout<<"现在没有下雨"<<endl; cout<<"========================="<<endl; }while ((c!='Y')&&(c!='y')&&(c!='N')&&(c!='n')); /*当bool表达式(c!='Y')&&(c!='y')&&(c!='N')&&(c!='n')为false时循环结束即，当(c!='Y')&&(c!='y')&&(c!='N')&&(c!='n')为true时意为c不等于Y且不等于y且不等于N且不等于n成立*/ system("pause");//暂停指令return 0; } //2-27 #include<iostream> using namespace std; int main() { int num,key=0; //定义两个整型变量num与key，其中key为循环结束标志，初始值为0 do { key=0; cout<<"你考了多少分？: "; cin>>num; cout<<endl; if ((num>=0)&&(num<60)) cout<<"差"<<endl; else if ((num>=60)&&(num<80)) cout<<"中"<<endl; else if ((num>=80)&&(num<90)) cout<<"良"<<endl; else if ((num>=90)&&(num<=100)) cout<<"优"<<endl; else key=1; if (key==1) cout<<"你输入的数据违法，请重新输入！"<<endl; cout<<"================================"<<endl; }while(key==1); //当key的值为1时循环继续，否则结束system("pause");//暂停指令return 0; } //2-28 #include<iostream> using namespace std; int main() { char c;//设置一个字符型变量c cout<<"Menu: A(dd) D(elete) S(ort) Q(uit),Select one: "; do { cin>>c; cout<<endl; switch (c) { case 'A': cout<<"The date have been add"<<endl; break;//从switch语句中跳出不再比较剩下的可能case 'D': cout<<"The date have been delete"<<endl; break; case 'S': cout<<"The date have been sort"<<endl; break; case 'Q': cout<<"Thank you for using this software!"<<endl; break; } cout<<"===================================================="<<endl; if ((c!='Q')&&((c=='A')||(c=='D')||(c=='S'))) //if语句的判断表达式可以是十分复杂的逻辑表达式cout<<"Please input your order: "; else if ((c!='A')&&(c!='D')&&(c!='S')&&(c!='Q')) cout<<"Your order is unlawful!Please input it again: "; }while(c!='Q'); return 0; } //2-29 #include<iostream> #include<cmath>//导入数学库，可以使用如开方函数sqrt之类的数学函数using namespace std; int main() { int i,j,k; cout<<'2'<<endl;//独立考虑2 for (i=3;i<=100;i++)//从3到100循环{ k=0; for (j=2;j<=static_cast<int>(sqrt(i));j++) //从2到取过整的i的开平方值循环if (i%j==0) //判断i是否可被j整除{ k=1;//k为判断标志变量，当i可被j整除，即j 是i的一个因数时，k赋1 break;//一旦出现i被j整除的情况从循环中跳出} if (k==0) cout<<i<<endl; } system("pause"); return 0; } //2-34 #include<iostream> using namespace std; int num(int x) { int i,j; j=1; for (i=1;i<=x;i++) j*=i; return j; } int main() { int n; int red,yellow,blue,white,black; cout<<"Please input the number of the balls"<<endl; cout<<"red,yellow,blue,white,black : "<<endl; cout<<"======================================"<<endl;cin>>red>>yellow>>blue>>white>>black;cout<<"======================================"<<endl;n=num(5)/num(3)/num(2)*red*yellow*blue*white*black; cout<<"There are "<<n<<" methods to get three kinds of the balls"<<endl; system("pause"); return 0; } //2-35 #include<iostream> #include<iomanip> //I/O函数库的头文件，可使用setw。

//注意：教材上打错了是iomanip不是iomainp ！！！using namespace std; int main() { int i,j; for (i=1;i<=9;i++) { for (j=i;j<=9;j++) { cout<<i<<'*'<<j<<'='; cout<<setw(2)<<i*j; cout<<' '; } cout<<endl; } system("pause"); return 0; } //3-9 #include<iostream> #include<cmath> using namespace std; bool zhishu(int n) { int i=2;bool t=true; while ( (n%i!=0)&&( i<(static_cast<int>( sqrt(n) ) ) ) ) { i++; } if (n%i==0) t=false; return t; } int main() { int n; cin>>n; if (n==1) cout <<"不是质数"; else if (n==2) cout<<"是质数"; else if (zhishu(n)==true) cout<<"是质数"; else cout<<"不是质数"; system("pause"); return 0; } //3-15 #include<iostream> using namespace std; int x; int p(int n) { if (n==0) return 1; else if (n==1) return x; else return (((2*n-1)*x*p(n-1)-(n-1)*p(n-2))/n); } int main() { int n; cout<<"Please input the date of 'n' and 'x' :"<<endl; cin>>n; cin>>x; cout<<p(n); system("pause"); return 0; } //4-9 #include<iostream> #include<cmath> using namespace std; class Rectangle { public: int getArea(); Rectangle(int a=0,int b=0,int c=0,int d=0) { x1=a; y1=b; x2=c; y2=d; } private: int x1,y1,x2,y2; }; int Rectangle::getArea() { return (x2-x1)*(y2-y1); } int main() { int a,b,c,d; cout<<"Please input the first point :"<<endl; cin>>a; cin>>b; cout<<"Please input the second point :"<<endl; cin>>c; cin>>d; Rectangle s(a,b,c,d); cout<<abs(s.getArea()); system("pause"); return 0; } //4-13 #include<iostream> using namespace std; class Circle { public: double getArea(); Circle(double r=0){radius=r;} private: double radius; }; double Circle::getArea() { return 3.14159265*radius*radius; } int main() { int r; cin>>r; cout<<endl; Circle cir(r); cout<<cir.getArea(); system("pause"); return 0; } //4-20 #include<iostream> using namespace std; class Complex { public: Complex(double x,double y) { a=x; b=y; } Complex(double x) { a=x; b=0; } void add(Complex t) { a+=t.a; b+=t.b; } void show() { cout<<a<<'+'<<b<<'i'<<endl; } private: double a,b; }; int main() { Complex c1(3,5); Complex c2=4.5; c1.add(c2); c1.show(); system("pause"); return 0; } //5-16 #include<iostream> using namespace std; class X; class Y { public: void g(X &x); }; class X { public: X(int j=0):i(j){} friend void Y::g(X &x); friend class Z; friend void h(X &x); void show(){cout<<i<<endl;} private: int i; }; void Y::g(X &x){x.i++;} void h(X &x){ x.i+=10; } class Z{ public: void f(X &x) {x.i+=5;} }; int main() { X x; x.show(); Y y; y.g(x); x.show(); Z z; z.f(x); x.show(); h(x); x.show(); system("pause"); return 0; }。